buffer: add fast api for isAscii & isUtf8

[anonrig]

Adds v8 fast api for IsUtf8 and IsAscii methods

isAscii benchmark: https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/1706/

                                                                        confidence improvement accuracy (*)   (**)  (***)
buffers/buffer-isascii.js input='hello world' length='long' n=20000000         ***     37.08 %       ±0.87% ±1.17% ±1.52%
buffers/buffer-isascii.js input='hello world' length='short' n=20000000        ***     36.83 %       ±0.86% ±1.15% ±1.51%

isUtf8 benchmark: https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/1708/

buffers/buffer-isutf8.js input='∀x∈ℝ: ⌈x⌉ = −⌊−x⌋' length='long' n=20000000         ***      1.95 %       ±0.22% ±0.29% ±0.38%
buffers/buffer-isutf8.js input='∀x∈ℝ: ⌈x⌉ = −⌊−x⌋' length='short' n=20000000        ***     65.95 %       ±2.35% ±3.13% ±4.08%
buffers/buffer-isutf8.js input='regular string' length='long' n=20000000            ***     42.16 %       ±4.05% ±5.39% ±7.02%
buffers/buffer-isutf8.js input='regular string' length='short' n=20000000           ***    121.41 %       ±1.15% ±1.54% ±2.02%

[Renegade334]

I believe FastApiTypedArray is on the way out? (#55452)

[anonrig]

We can move to Local once V8 removes it

[Renegade334]

That moment is now: it is not present in V8 13.6, and #57753 is removing all remaining uses of it across the codebase.

[anonrig]

Ah, I'll update the implementation. Nice catch. Thanks @Renegade334

[codecov]

Codecov Report

Attention: Patch coverage is 88.23529% with 2 lines in your changes missing coverage. Please review.

Project coverage is 90.21%. Comparing base (e0cf8ae) to head (b28834c).
Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_buffer.cc	88.23%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #58058      +/-   ##
==========================================
+ Coverage   90.18%   90.21%   +0.02%     
==========================================
  Files         630      630              
  Lines      186393   186406      +13     
  Branches    36595    36614      +19     
==========================================
+ Hits       168103   168163      +60     
+ Misses      11090    11059      -31     
+ Partials     7200     7184      -16     

Files with missing lines	Coverage Δ
src/node_external_reference.h	100.00% <ø> (ø)
src/node_buffer.cc	67.79% <88.23%> (+0.28%)	⬆️

... and 32 files with indirect coverage changes

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[mcollina]

lgtm