buffer: add Buffer.fromHex() and Buffer.fromBase64()

[LiviaMedeiros]

These methods are already present on Uint8Array, so without defining them on Buffer they return instances of Uint8Array. This introduces wrapper to return instances of Buffer instead.

Fixes: #61146

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.55%. Comparing base (55600e6) to head (9c4e4c2).
⚠️ Report is 26 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #61157      +/-   ##
==========================================
+ Coverage   88.52%   88.55%   +0.02%     
==========================================
  Files         703      704       +1     
  Lines      208589   208810     +221     
  Branches    40226    40281      +55     
==========================================
+ Hits       184650   184908     +258     
+ Misses      15954    15926      -28     
+ Partials     7985     7976       -9     

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

... and 40 files with indirect coverage changes

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[avivkeller]

Remember to update the docs

[avivkeller]

Other than this is missing a doc entry, LGTM

[LiviaMedeiros]

Agreed, added to the docs.
Initially i intentionally omitted it because these are basically inherited from Uint8Array (we don't document Buffer.prototype.at() whatsoever), but it's worth adding to indicate that these are similar-but-different from Buffer.from(string, encoding).

[avivkeller]

Docs + impl lgtm

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/70610/

[aduh95]

Should we define those only if --no-js-base-64 as it is the case today?

$ node --no-js-base-64 -p 'Buffer.fromHex'                         
undefined
$ node -p 'Buffer.fromHex'    
[Function: fromHex]

[aduh95]

I don't think lazy loading makes sense here, I don't see what's the upside. Why not put it under an if statement instead?

$ ./node -p '"fromHex" in Buffer'
true
$ ./node --no-js-base-64 -p '"fromHex" in Buffer'
false

[LiviaMedeiros]

@aduh95 IIUC buffer.js is a part of early bootstrap, which is why getOptionValue('--js-base-64') is not available yet, and Uint8Array.{fromHex,fromBase64} are still undefined even when the feature is enabled. Neither

'fromHex' in Uint8Array
Uint8Array.fromHex !== undefined
typeof Uint8Array.fromHex !== 'undefined'
const { Uint8Array: { fromHex } } = primordials
const { globalThis: { Uint8Array: { fromHex } } } = primordials
const { Uint8Array: { fromHex } } = globalThis

gives anything meaningful.
If I'm missing something and it is possible to check synchronously, please let me know, I'd be happy to replace it with if.

[targos]

Why do we care about --js-base-64? We only explicitly support a small subset of V8 flags and I don't see a compelling reason in this case.