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 84.90566% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.05%. Comparing base (8c6e39e) to head (5bac588).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/streams/iter/pull.js	84.90%	8 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #63318   +/-   ##
=======================================
  Coverage   90.05%   90.05%           
=======================================
  Files         714      714           
  Lines      225564   225612   +48     
  Branches    42660    42668    +8     
=======================================
+ Hits       203134   203184   +50     
- Misses      14209    14216    +7     
+ Partials     8221     8212    -9     

Files with missing lines	Coverage Δ
lib/internal/streams/iter/pull.js	85.14% <84.90%> (-0.10%)	⬇️

... and 28 files with indirect coverage changes

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[jasnell]

LGTM with a question

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/73485/

[trivikr]

Re-requested reviews because of rebase which involved resolving conflicts.