buffer: use simdutf for two-byte utf8 byteLength

[mertcanaltin]

I changed two-byte (UTF-16) string path, we are now switching from V8 Utf8LengthV2 to simdutf,

note: simdutf is only enabled for two-byte strings containing 512 code units or more

benchmark results:

➜  node git:(mert/buffer-bytelength-utf8-simdutf) ✗ node-benchmark-compare /tmp/nvb/result2.csv
                                                                                            confidence improvement accuracy (*)   (**)  (***)
buffers/buffer-bytelength-string.js n=4000000 repeat=1 encoding='utf8' type='four_bytes'                    0.56 %       ±1.66% ±2.21% ±2.87%
buffers/buffer-bytelength-string.js n=4000000 repeat=1 encoding='utf8' type='latin1'                        0.45 %       ±1.50% ±2.00% ±2.61%
buffers/buffer-bytelength-string.js n=4000000 repeat=1 encoding='utf8' type='one_byte'                      1.49 %       ±1.85% ±2.46% ±3.21%
buffers/buffer-bytelength-string.js n=4000000 repeat=1 encoding='utf8' type='three_bytes'                   0.02 %       ±1.40% ±1.87% ±2.45%
buffers/buffer-bytelength-string.js n=4000000 repeat=1 encoding='utf8' type='two_bytes'                     0.96 %       ±1.37% ±1.82% ±2.37%
buffers/buffer-bytelength-string.js n=4000000 repeat=16 encoding='utf8' type='four_bytes'          ***     28.95 %       ±1.10% ±1.47% ±1.92%
buffers/buffer-bytelength-string.js n=4000000 repeat=16 encoding='utf8' type='latin1'                *     -0.74 %       ±0.59% ±0.79% ±1.03%
buffers/buffer-bytelength-string.js n=4000000 repeat=16 encoding='utf8' type='one_byte'                     0.14 %       ±1.41% ±1.88% ±2.45%
buffers/buffer-bytelength-string.js n=4000000 repeat=16 encoding='utf8' type='three_bytes'          **      2.25 %       ±1.66% ±2.21% ±2.88%
buffers/buffer-bytelength-string.js n=4000000 repeat=16 encoding='utf8' type='two_bytes'                    1.38 %       ±1.73% ±2.30% ±2.99%
buffers/buffer-bytelength-string.js n=4000000 repeat=2 encoding='utf8' type='four_bytes'             *     -1.44 %       ±1.35% ±1.80% ±2.34%
buffers/buffer-bytelength-string.js n=4000000 repeat=2 encoding='utf8' type='latin1'                        0.09 %       ±1.29% ±1.72% ±2.24%
buffers/buffer-bytelength-string.js n=4000000 repeat=2 encoding='utf8' type='one_byte'                     -0.77 %       ±1.77% ±2.36% ±3.07%
buffers/buffer-bytelength-string.js n=4000000 repeat=2 encoding='utf8' type='three_bytes'                   0.86 %       ±1.65% ±2.20% ±2.86%
buffers/buffer-bytelength-string.js n=4000000 repeat=2 encoding='utf8' type='two_bytes'              *     -1.69 %       ±1.61% ±2.14% ±2.78%
buffers/buffer-bytelength-string.js n=4000000 repeat=256 encoding='utf8' type='four_bytes'         ***     36.25 %       ±1.23% ±1.65% ±2.19%
buffers/buffer-bytelength-string.js n=4000000 repeat=256 encoding='utf8' type='latin1'                     -0.20 %       ±0.24% ±0.32% ±0.41%
buffers/buffer-bytelength-string.js n=4000000 repeat=256 encoding='utf8' type='one_byte'             *     -0.72 %       ±0.63% ±0.84% ±1.10%
buffers/buffer-bytelength-string.js n=4000000 repeat=256 encoding='utf8' type='three_bytes'        ***     67.59 %       ±1.42% ±1.91% ±2.52%
buffers/buffer-bytelength-string.js n=4000000 repeat=256 encoding='utf8' type='two_bytes'          ***     67.62 %       ±1.23% ±1.65% ±2.18%

Be aware that when doing many comparisons the risk of a false-positive result increases.
In this case, there are 20 comparisons, you can thus expect the following amount of false-positive results:
  1.00 false positives, when considering a   5% risk acceptance (*, **, ***),
  0.20 false positives, when considering a   1% risk acceptance (**, ***),
  0.02 false positives, when considering a 0.1% risk acceptance (***)
➜  node git:(mert/buffer-bytelength-utf8-simdutf) ✗

[codecov]

Codecov Report

❌ Patch coverage is 52.38095% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.30%. Comparing base (4d21e86) to head (f382a03).
⚠️ Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_buffer.cc	52.38%	8 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #63639      +/-   ##
==========================================
+ Coverage   90.29%   90.30%   +0.01%     
==========================================
  Files         730      730              
  Lines      234773   234821      +48     
  Branches    43953    43959       +6     
==========================================
+ Hits       211996   212066      +70     
+ Misses      14495    14484      -11     
+ Partials     8282     8271      -11     

Files with missing lines	Coverage Δ
src/node_buffer.cc	68.10% <52.38%> (-0.28%)	⬇️

... and 39 files with indirect coverage changes

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[mcollina]

lgtm