feat: support doc comments in Motoko bindgen

[christoph-dfinity]

Overview
Adds support for reflecting doc comments from Candid declaration files to the Motoko generated bindings.

Internally, it adds the IDLMergedProg which is constructed when parsing the Candid declarations and is passed to the Motoko bindings generator. It containts the syntax types along with the associated comments, and it's traversed in parallel with the inner types by the binding generator.

Follow-up PRs will add support for doc comments in the other bindings generators.

Closes #625.

[github-actions]

Name	Max Mem (Kb)	Encode	Decode
blob	4_224	4_206_559	2_121_055 ($\textcolor{green}{-0.00\%}$)
btreemap	75_456	4_261_360_630	15_191_359_361 ($\textcolor{green}{-0.33\%}$)
nns	192	1_966_454 ($\textcolor{green}{-0.01\%}$)	5_468_145 ($\textcolor{green}{-0.03\%}$)
nns_list_proposal	1_088	6_814_372 ($\textcolor{red}{0.00\%}$)	66_996_590 ($\textcolor{green}{-1.29\%}$)
option_list	128	7_481_063 ($\textcolor{red}{0.08\%}$)	25_531_164 ($\textcolor{green}{-0.95\%}$)
text	6_336	4_203_506	7_877_219 ($\textcolor{green}{-0.00\%}$)
variant_list	128	7_537_258 ($\textcolor{red}{0.08\%}$)	24_121_592 ($\textcolor{green}{-0.57\%}$)
vec_int16	16_704	123_693_002	1_019_238_917 ($\textcolor{green}{-4.71\%}$)

• Parser cost: 15_211_448 ($\textcolor{red}{0.01\%}$)
• Extra args: 3_165_441 ($\textcolor{red}{0.59\%}$)

Click to see raw report

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Benchmark: blob
  total:
    instructions: 6.33 M (-0.00%) (change within noise threshold)
    heap_increase: 66 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 4.21 M (no change)
    heap_increase: 66 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 2.12 M (-0.00%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: text
  total:
    instructions: 12.08 M (-0.00%) (change within noise threshold)
    heap_increase: 99 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 4.20 M (no change)
    heap_increase: 66 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 7.88 M (-0.00%) (change within noise threshold)
    heap_increase: 33 pages (no change)
    stable_memory_increase: 0 pages (no change)

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Benchmark: vec_int16
  total:
    instructions: 1.14 B (improved by 4.22%)
    heap_increase: 261 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 123.69 M (no change)
    heap_increase: 261 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 1.02 B (improved by 4.71%)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap
  total:
    instructions: 19.45 B (-0.26%) (change within noise threshold)
    heap_increase: 1179 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 4.26 B (no change)
    heap_increase: 159 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 15.19 B (-0.33%) (change within noise threshold)
    heap_increase: 1020 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: option_list
  total:
    instructions: 33.01 M (-0.72%) (change within noise threshold)
    heap_increase: 2 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 7.48 M (0.08%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 25.53 M (-0.95%) (change within noise threshold)
    heap_increase: 2 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: variant_list
  total:
    instructions: 31.66 M (-0.41%) (change within noise threshold)
    heap_increase: 2 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 7.54 M (0.08%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 24.12 M (-0.57%) (change within noise threshold)
    heap_increase: 2 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: nns
  total:
    instructions: 23.49 M (-0.00%) (change within noise threshold)
    heap_increase: 3 pages (no change)
    stable_memory_increase: 0 pages (no change)

  0. Parsing (scope):
    calls: 1 (no change)
    instructions: 15.21 M (0.01%) (change within noise threshold)
    heap_increase: 3 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 1.97 M (-0.01%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 5.47 M (-0.03%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: nns_list_proposal
  total:
    instructions: 73.81 M (-1.17%) (change within noise threshold)
    heap_increase: 17 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 6.81 M (0.00%) (change within noise threshold)
    heap_increase: 3 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 67.00 M (-1.29%) (change within noise threshold)
    heap_increase: 14 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: extra_args
  total:
    instructions: 3.17 M (0.59%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Summary:
  instructions:
    status:   Improvements detected 🟢
    counts:   [total 9 | regressed 0 | improved 1 | new 0 | unchanged 8]
    change:   [max +18.60K | p75 -10 | median -130.93K | p25 -875.77K | min -50.33M]
    change %: [max +0.59% | p75 -0.00% | median -0.26% | p25 -0.72% | min -4.22%]

  heap_increase:
    status:   No significant changes 👍
    counts:   [total 9 | regressed 0 | improved 0 | new 0 | unchanged 9]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  stable_memory_increase:
    status:   No significant changes 👍
    counts:   [total 9 | regressed 0 | improved 0 | new 0 | unchanged 9]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

---------------------------------------------------

Only significant changes:
| status | name                   | calls |   ins |  ins Δ% |  HI |  HI Δ% | SMI |  SMI Δ% |
|--------|------------------------|-------|-------|---------|-----|--------|-----|---------|
|   -    | vec_int16              |       | 1.14B |  -4.22% | 261 |  0.00% |   0 |   0.00% |
|   -    | vec_int16::2. Decoding |     1 | 1.02B |  -4.71% |   0 |  0.00% |   0 |   0.00% |

ins = instructions, HI = heap_increase, SMI = stable_memory_increase, Δ% = percent change

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Successfully persisted results to canbench_results.yml