src: define O_SYNC, O_DSYNC and O_DIRECT on Windows

[PickBas]

src: define O_SYNC, O_DSYNC and O_DIRECT on Windows

These POSIX open-flag names have no macro in the Windows C runtime, so they were missing from fs.constants on Windows and got silently dropped when passed to fs.open(). libuv already honors the underlying flags (FILE_FLAG_WRITE_THROUGH for sync, FILE_FLAG_NO_BUFFERING for direct), so this just exposes the constants under their portable names wired to libuv's values.

Portable code requesting synchronized or unbuffered I/O now works on Windows instead of losing the flag.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.12%. Comparing base (874e96e) to head (3171100).
⚠️ Report is 485 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #64707      +/-   ##
==========================================
- Coverage   90.24%   90.12%   -0.13%     
==========================================
  Files         739      741       +2     
  Lines      241676   242251     +575     
  Branches    45544    45621      +77     
==========================================
+ Hits       218102   218329     +227     
- Misses      15101    15427     +326     
- Partials     8473     8495      +22     

Files with missing lines	Coverage Δ
src/node_constants.cc	99.71% <ø> (ø)

... and 104 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75966/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75984/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75988/