stream: run a replaced write() in the flowing pipe

[nigrosimone]

pipe() calls dest.write(), but since #66182 a flowing pipe whose source pushes from _read() hands each chunk to dest._write() directly. A write() replaced on the destination, or overridden in a subclass, no longer runs.

Found on 26.11.1 with a framework whose response is a stream.Writable: compression middleware replaces res.write(), and a file piped to the response came out as a gzip body with uncompressed chunks in it (Z_DATA_ERROR on the client). 26.10.0 is fine.

Fix: take the fast path only when write() is Writable.prototype.write.

Test: test/parallel/test-stream-pipe-replaced-write.js, one write() replaced on the instance and one in a subclass. It fails on 26.11.1 (1 call to write() out of 64) and passes with the fix.

cc @anonrig

Disclosure: I used Opus 5.5 (Max) as coding assistant

[nodejs-github-bot]

Review requested:

• @nodejs/streams

[mcollina]

@nigrosimone this seems good, why it's draft?

[nigrosimone]

@mcollina my local build is still running, I want to see the test pass there first. Ready in about an hour, or I can mark it ready now and let the CI run, if you prefer.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.44%. Comparing base (6d5e309) to head (d603f99).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #66596   +/-   ##
=======================================
  Coverage   90.44%   90.44%           
=======================================
  Files         791      791           
  Lines      276562   276565    +3     
  Branches    53126    53116   -10     
=======================================
+ Hits       250130   250138    +8     
+ Misses      16846    16834   -12     
- Partials     9586     9593    +7     

Files with missing lines	Coverage Δ
lib/internal/streams/writable.js	96.43% <100.00%> (+<0.01%)	⬆️

... and 30 files with indirect coverage changes

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