stream: reject nested async streamables in from()

[trivikr]

Fixes: #64351

This updates stream/iter.from() so the sync-iterable fallback rejects
nested async-only streamables. When from() consumes a sync iterable, nested
async iterables and toAsyncStreamable values now throw
ERR_INVALID_ARG_TYPE instead of being consumed.

Promise values yielded by sync iterables are still awaited.

---

Assisted-by: openai:gpt-5.5

[nodejs-github-bot]

Review requested:

• @nodejs/streams

[codecov]

Codecov Report

❌ Patch coverage is 77.77778% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.23%. Comparing base (8e1ab55) to head (2e3bde5).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/streams/iter/from.js	77.77%	4 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #64352   +/-   ##
=======================================
  Coverage   90.23%   90.23%           
=======================================
  Files         741      741           
  Lines      240979   240988    +9     
  Branches    45395    45409   +14     
=======================================
+ Hits       217450   217464   +14     
  Misses      15112    15112           
+ Partials     8417     8412    -5     

Files with missing lines	Coverage Δ
lib/internal/streams/iter/from.js	88.25% <77.77%> (+0.16%)	⬆️

... and 23 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/74659/