stream: add sync iterable fast path to pipeTo

[trivikr]

Description

This adds a pipeTo() fast path for synchronous iterable sources when there
are no transforms, no abort signal, and the writer supports writeSync().

Previously, pipeTo() always normalized through from(), which routes sync
iterables through the async normalization path. The new guarded path writes
incrementally from the sync iterator while preserving async fallback behavior
for values that still require async normalization.

Benchmark

                                                                               confidence improvement accuracy (*)    (**)   (***)
streams/iter-throughput-pipeto.js n=5 datasize=1048576 api='iter-sync-source'         ***     18.03 %       ±3.54%  ±4.86%  ±6.64%
streams/iter-throughput-pipeto.js n=5 datasize=16777216 api='iter-sync-source'                 7.09 %      ±19.35% ±27.78% ±40.79%
streams/iter-throughput-pipeto.js n=5 datasize=67108864 api='iter-sync-source'        ***     10.86 %       ±3.77%  ±5.23%  ±7.26%

---

Assisted-by: openai:gpt-5.5

[nodejs-github-bot]

Review requested:

• @nodejs/performance
• @nodejs/streams

[codecov]

Codecov Report

❌ Patch coverage is 85.45455% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.07%. Comparing base (2edd842) to head (004031e).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/streams/iter/pull.js	85.45%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #63318      +/-   ##
==========================================
+ Coverage   90.04%   90.07%   +0.02%     
==========================================
  Files         714      714              
  Lines      225338   225388      +50     
  Branches    42598    42628      +30     
==========================================
+ Hits       202897   203009     +112     
+ Misses      14236    14155      -81     
- Partials     8205     8224      +19     

Files with missing lines	Coverage Δ
lib/internal/streams/iter/pull.js	85.10% <85.45%> (-0.06%)	⬇️

... and 38 files with indirect coverage changes

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