stream: settle pending stream iter reads on return

[trivikr]

This updates stream/iter cleanup so pending next() calls are settled when
a consumer calls return().

Previously, push() and broadcast() could leave a pending next() promise
unresolved if return() was called before any chunk was written. The cleanup
paths now resolve those pending reads with { done: true, value: undefined }.

Regression coverage was added for both push() and broadcast().

Fixes: #63519

---

Assisted-by: openai:gpt-5.5

[nodejs-github-bot]

Review requested:

• @nodejs/streams

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.32%. Comparing base (92f48f4) to head (4c2a5f1).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #63521      +/-   ##
==========================================
+ Coverage   90.31%   90.32%   +0.01%     
==========================================
  Files         730      730              
  Lines      234653   234662       +9     
  Branches    43952    43954       +2     
==========================================
+ Hits       211926   211970      +44     
+ Misses      14474    14420      -54     
- Partials     8253     8272      +19     

Files with missing lines	Coverage Δ
lib/internal/streams/iter/broadcast.js	85.25% <100.00%> (+0.01%)	⬆️
lib/internal/streams/iter/push.js	92.09% <100.00%> (+0.08%)	⬆️

... and 32 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/73637/