stream: fix isErrored/isWritable for WritableStreams

[Renegade334]

The underlying machinery for these was missed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.54%. Comparing base (6274eb7) to head (ace0284).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #60905      +/-   ##
==========================================
- Coverage   88.55%   88.54%   -0.01%     
==========================================
  Files         703      703              
  Lines      208291   208301      +10     
  Branches    40170    40162       -8     
==========================================
- Hits       184443   184436       -7     
+ Misses      15874    15873       -1     
- Partials     7974     7992      +18     

Files with missing lines	Coverage Δ
lib/internal/webstreams/writablestream.js	99.85% <100.00%> (+<0.01%)	⬆️

... and 44 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/70356/