feat: Actually decode dictionary arrays

[paleolimbot]

This PR uses the previous steps to output arrays (including the ArrowArrayStream reader). This lets us wire it in to all the tests as well.

The main follow up is that this PR currently deep copies the dictionary for every batch that arrives, negating much of the point of dictionary encoding. This is a fairly self-contained change that I'll do separately: #864

I also added dictionary index validation while I was here! It is fairly compact (compared to the other code).

Closes #845.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 60.97561% with 48 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.44%. Comparing base (f11d517) to head (282727e).
⚠️ Report is 37 commits behind head on main.

Files with missing lines	Patch %	Lines
src/nanoarrow/ipc/decoder.c	52.94%	12 Missing and 20 partials ⚠️
src/nanoarrow/ipc/reader.c	70.90%	8 Missing and 8 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #861      +/-   ##
==========================================
- Coverage   79.96%   79.44%   -0.53%     
==========================================
  Files         105      106       +1     
  Lines       15461    15881     +420     
  Branches     1738     1834      +96     
==========================================
+ Hits        12364    12616     +252     
- Misses       1998     2115     +117     
- Partials     1099     1150      +51     

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[paleolimbot]

I'm pretty happy with this! If there are no objections I'll merge later today and move on to the shared dictionary problem.