quic: allow null body when opening streams

[efekrskl]

createBidirectionalStream({ body: null }) was documented as valid but is rejected. This PR allows passing null as body which is also supported in setBody and a regression test

[nodejs-github-bot]

Review requested:

• @nodejs/quic

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.47%. Comparing base (a7a96c2) to head (f4a0587).
⚠️ Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #66690      +/-   ##
==========================================
- Coverage   90.47%   90.47%   -0.01%     
==========================================
  Files         791      791              
  Lines      277088   277089       +1     
  Branches    53286    53279       -7     
==========================================
- Hits       250703   250689      -14     
- Misses      16805    16817      +12     
- Partials     9580     9583       +3     

Files with missing lines	Coverage Δ
lib/internal/quic/quic.js	100.00% <100.00%> (ø)

... and 32 files with indirect coverage changes

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[pimterry]

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/78363/