stream: settle pending broadcast reads on return

[trivikr]

This updates broadcast async iterator cleanup so a pending
next() settles when the consumer is returned.

When a broadcast consumer has an outstanding next() and
return() is called before data arrives, the pending read is now
resolved with { done: true, value: undefined } during detach.

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 90.31%. Comparing base (4639dcb) to head (273ae63).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #63603      +/-   ##
==========================================
+ Coverage   90.29%   90.31%   +0.02%     
==========================================
  Files         730      730              
  Lines      234695   234696       +1     
  Branches    43956    43954       -2     
==========================================
+ Hits       211927   211976      +49     
+ Misses      14494    14431      -63     
- Partials     8274     8289      +15     

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

... and 48 files with indirect coverage changes

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