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

❌ Patch coverage is 37.50000% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.31%. Comparing base (8257091) to head (f4a87a4).

Files with missing lines	Patch %	Lines
lib/internal/streams/iter/push.js	28.57%	5 Missing ⚠️

Additional details and impacted files

@@ Coverage Diff @@## main #63521 +/- ##
==========================================
- Coverage 90.32% 90.31% -0.01% 
==========================================
Files 730 730 Lines 234671 234679 +8 Branches 43946 43950 +4 ==========================================
- Hits 211965 211954 -11 - Misses 14423 14436 +13 - Partials 8283 8289 +6 

Files with missing lines	Coverage Δ
lib/internal/streams/iter/broadcast.js	85.25% <100.00%> (+0.01%)	⬆️
lib/internal/streams/iter/push.js	91.00% <28.57%> (-0.58%)	⬇️

... and 29 files with indirect coverage changes

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[nodejs-github-bot]

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

[trivikr]

The bug in push was fixed in #63555, when fixing for iterator.throw()

I posted a new broadcast only specific PR at #63603