buffer: add isByteString

[jasnell]

Implements a fast check to determine if a string is Latin1 a byte string.

Can be many times faster than the equivalent regex check.

input	isByteString	regex	loop
short, one-byte	232M	122M	55M
short, two-byte	207M	130M	56M
short, invalid	106M	48M	53M
long, one-byte	221M	93M	230k
long, two-byte	6.7M	913k	186k
long, invalid	75M	914k	234k

(the larger perf gap there is with concatenated strings)

[nodejs-github-bot]

Review requested:

• @nodejs/performance

[aduh95]

I don't think isLatin1 is a good name, \u0100 can definitely be a 2-byte latin1 string

[jasnell]

Yeah, I'm going to rename to isByteString ... it matches the webidl usage better.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/77917/ 💚

[codecov]

Codecov Report

❌ Patch coverage is 85.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.37%. Comparing base (8bf65d4) to head (090b087).
⚠️ Report is 13 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_buffer.cc	76.92%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #66298      +/-   ##
==========================================
+ Coverage   90.36%   90.37%   +0.01%     
==========================================
  Files         790      790              
  Lines      273842   273876      +34     
  Branches    52386    52393       +7     
==========================================
+ Hits       247453   247523      +70     
+ Misses      16881    16852      -29     
+ Partials     9508     9501       -7     

Files with missing lines	Coverage Δ
lib/buffer.js	99.74% <100.00%> (+<0.01%)	⬆️
src/node_buffer.cc	70.40% <76.92%> (+0.06%)	⬆️

... and 30 files with indirect coverage changes

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