buffer: return fastbuffer directly instead of buffer.alloc(0)

[gurgunday]

As in other places here, we don't need to call Buffer.alloc(0), which validates the length and calls FastBuffer anyway

This bypasses the validation logic and is consequently faster

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.58%. Comparing base (d9cf867) to head (e12c1a8).
⚠️ Report is 49 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #60398      +/-   ##
==========================================
- Coverage   88.58%   88.58%   -0.01%     
==========================================
  Files         704      704              
  Lines      207815   207815              
  Branches    40036    40041       +5     
==========================================
- Hits       184102   184083      -19     
- Misses      15758    15770      +12     
- Partials     7955     7962       +7     

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

... and 39 files with indirect coverage changes

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[ChALkeR]

Perhaps you also want to replace Buffer.allocUnsafe(0) likewise

[gurgunday]

Closed in favor of #60558

[ChALkeR]

@gurgunday why not though?

[gurgunday]

Didn't you see my comment?

Closed in favor of #60558

[ChALkeR]

@gurgunday I mean the thumbs down on

Perhaps you also want to replace Buffer.allocUnsafe(0) likewise

Which I interpreted as "No", but curious why (which is why I asked)

[gurgunday]

Oh, sorry - I only saw one instance of that and it's allocated once during bootstrap

[ChALkeR]

Ah, the rest are in undici, where this wouldn't be possible directly, I see...
Thanks!