zlib: improve zstd decoding across chunk boundaries

[jasnell]

Discovered when testing some other changes that zstd was not handling certain chunk boundaries very well. This fixes it.

• Decodes concatenated and skippable zstd frames across all chunk boundaries.
• Preserves rejectGarbageAfterEnd semantics.
• Reports corruption in subsequent frames.
• Handles trailing partial frame identifiers consistently.
• Covers classic sync/async and iterable APIs.
• Updated documentation and internal typings.

Technically a behavior change but zstd is still experimental.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/77112/

[codecov]

Codecov Report

❌ Patch coverage is 91.46341% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.19%. Comparing base (8af7545) to head (461b2a7).
⚠️ Report is 21 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_zlib.cc	90.41%	2 Missing and 5 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #65865   +/-   ##
=======================================
  Coverage   90.18%   90.19%           
=======================================
  Files         771      771           
  Lines      264619   264687   +68     
  Branches    50231    50256   +25     
=======================================
+ Hits       238653   238735   +82     
+ Misses      16961    16952    -9     
+ Partials     9005     9000    -5     

Files with missing lines	Coverage Δ
lib/zlib.js	98.15% <100.00%> (+<0.01%)	⬆️
src/node_zlib.cc	79.91% <90.41%> (+0.72%)	⬆️

... and 27 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/77141/