Better Bolt 11 parsing spec compliance

[t-bast]

Add more Bolt 11 spec tests.
Ignore hashed fields with invalid length as the spec requires:

A reader:
    * MUST skip over unknown fields, OR an f field with unknown version, OR p, h, s or n fields that do NOT have data_lengths of 52, 52, 52 or 53, respectively.

See lightning/bolts#699 and lightning/bolts#736.

[codecov-io]

Codecov Report

Merging #1302 into master will increase coverage by 0.83%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1302      +/-   ##
==========================================
+ Coverage   77.52%   78.35%   +0.83%     
==========================================
  Files         144      144              
  Lines       10098    10756     +658     
  Branches      390      429      +39     
==========================================
+ Hits         7828     8428     +600     
- Misses       2270     2328      +58

Impacted Files	Coverage Δ
...scala/fr/acinq/eclair/payment/PaymentRequest.scala	93.03% <100%> (+0.48%)	⬆️
...clair/blockchain/electrum/ElectrumClientPool.scala	78.49% <0%> (-6.46%)	⬇️
...cala/fr/acinq/eclair/db/sqlite/SqliteAuditDb.scala	99.24% <0%> (+0.17%)	⬆️
...r/acinq/eclair/payment/send/PaymentInitiator.scala	96.77% <0%> (+0.22%)	⬆️
...nq/eclair/blockchain/electrum/ElectrumClient.scala	73.64% <0%> (+0.36%)	⬆️
...in/scala/fr/acinq/eclair/api/JsonSerializers.scala	96% <0%> (+0.54%)	⬆️
...c/main/scala/fr/acinq/eclair/channel/Helpers.scala	95.36% <0%> (+0.77%)	⬆️
...c/main/scala/fr/acinq/eclair/payment/Auditor.scala	95.49% <0%> (+1.3%)	⬆️
...r-core/src/main/scala/fr/acinq/eclair/Eclair.scala	55.78% <0%> (+1.75%)	⬆️
...c/main/scala/fr/acinq/eclair/channel/Channel.scala	85.94% <0%> (+2.38%)	⬆️
... and 3 more

[pm47]

I think I have another idea, will try and let you know.

[pm47]

Nice catch

[pm47]

Here is my take: #1308.

[t-bast]

Closing in favor of #1308