src: report libuv error when openAsBlob cannot stat

[bitpshr]

Fixes: #65514

FdEntry::Create() dropped the uv_fs_stat() status and returned nullptr, so BlobFromFilePath() reported every failure as ERR_INVALID_ARG_VALUE: Unable to open file as blob. A missing file is not a malformed argument, and the TypeError had no errno, syscall, or path to work with. This threads the status out and throws a UVException instead:

$ node -e 'require("fs").openAsBlob("./nope.txt")'
# before: TypeError [ERR_INVALID_ARG_VALUE]: Unable to open file as blob
# after:  Error: ENOENT: no such file or directory, stat './nope.txt'

which matches what fs.stat() reports for the same path, errno/syscall/path included.

Two notes:

• The reported EACCES case does not actually reach this path. stat only needs traversal permission on the parent, so an unreadable file still opens fine and fails later at read time with NotReadableError. The stat failures this affects are ENOENT, ENOTDIR, ELOOP and friends.
• fs: fix always return promise from fs.openAsBlob #62655 fixes the separate sync-throw half of fs.openAsBlob reports a missing file as ERR_INVALID_ARG_VALUE, discarding the ENOENT #65514 and its new test asserts ERR_INVALID_ARG_VALUE for a missing file, which would need updating if that lands after this. I wrote the test here as assert.rejects(async () => openAsBlob(missing), ...) so it passes either way, and I am happy to fold this into that PR instead if the reviewers there would rather keep it in one place.

I also left the directory case alone (openAsBlob("./some-dir") still succeeds and fails at read time). There is an existing TODO(@jasnell, @flakey5) on FdEntry about rejecting non-regular files, and that felt like a separate behavior change rather than something to slip in here. Glad to take it on as a follow-up.

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 90.16%. Comparing base (46a7dbd) to head (0e065fe).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/dataqueue/queue.cc	83.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #65517      +/-   ##
==========================================
- Coverage   90.21%   90.16%   -0.06%     
==========================================
  Files         751      751              
  Lines      253550   253589      +39     
  Branches    47813    47782      -31     
==========================================
- Hits       228733   228640      -93     
- Misses      16076    16207     +131     
- Partials     8741     8742       +1     

Files with missing lines	Coverage Δ
src/node_blob.cc	73.29% <100.00%> (+0.59%)	⬆️
src/dataqueue/queue.cc	67.74% <83.33%> (-0.20%)	⬇️

... and 31 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.