zlib: prevent oversized ArrayBuffer retention in one-shot methods

[Abhirup0]

Fixes: #65600

When one-shot convenience methods (zlib.gzip(), zlib.deflate(),
zlib.brotliCompress(), zlib.zstdCompress(), etc.) complete with a single
output chunk, zlibBufferOnEnd and processChunkSync returned bufs[0],
which was a sub-slice of the 16 KB default _outBuffer. For small outputs,
this retained the full 16,384-byte backing ArrayBuffer.

Because this.close() synchronously frees the native C++ context and
decrements the external memory accounter back to 0, V8 does not observe
external memory pressure or significant JS heap growth. In long-running
processes with comfortable heaps, dead ArrayBuffer allocations accumulated
until the process ran out of memory.

This change:

1. Trims single-chunk one-shot results to exact size with Buffer.from() when
   the chunk is smaller than its backing ArrayBuffer.
2. Releases internal references to _outBuffer, buffers, cb, and
   _writeState on stream completion, error, and close.

[MikeMcC399]

This PR fails many tests.

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[codecov]

Codecov Report

❌ Patch coverage is 90.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.05%. Comparing base (7b0de5e) to head (d9ac576).
⚠️ Report is 10 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/zlib.js	90.00%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #65647      +/-   ##
==========================================
- Coverage   90.05%   90.05%   -0.01%     
==========================================
  Files         754      754              
  Lines      255722   255742      +20     
  Branches    48314    48317       +3     
==========================================
+ Hits       230281   230298      +17     
- Misses      16555    16565      +10     
+ Partials     8886     8879       -7     

Files with missing lines	Coverage Δ
lib/zlib.js	97.99% <90.00%> (-0.15%)	⬇️

... and 37 files with indirect coverage changes

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[Abhirup0]

Updated the commit to follow commit message line wrapping and DCO sign-off guidelines, updated the test suite to use common.mustSucceed(), and narrowed the implementation cleanly to the single-chunk buffer trimming in zlibBufferOnEnd and processChunkSync. CI checks should now be green.