path: remove StringPrototypeCharCodeAt from posix.extname

[RedYetiDev]

Benchmark shows an improvement:

                                                                                confidence improvement accuracy (*)   (**)   (***)
path/extname-posix.js n=100000 path=''                                                  *      5.10 %       ±4.68% ±6.23%  ±8.14%
path/extname-posix.js n=100000 path='/'                                                 *      4.92 %       ±3.78% ±5.04%  ±6.55%
path/extname-posix.js n=100000 path='/foo'                                              *      6.57 %       ±6.24% ±8.32% ±10.88%
path/extname-posix.js n=100000 path='/foo/bar/baz/asdf/quux.foobarbazasdfquux'        ***      7.94 %       ±2.34% ±3.12%  ±4.08%
path/extname-posix.js n=100000 path='/foo/bar/baz/asdf/quux'                            *      5.77 %       ±4.68% ±6.24%  ±8.15%
path/extname-posix.js n=100000 path='foo/.bar.baz'                                      *      4.49 %       ±4.40% ±5.88%  ±7.69%
path/extname-posix.js n=100000 path='foo/bar/...baz.quux'                             ***     11.69 %       ±6.29% ±8.37% ±10.90%
path/extname-posix.js n=100000 path='foo/bar/..baz.quux'                               **      7.95 %       ±5.30% ±7.05%  ±9.17%
path/extname-posix.js n=100000 path='index.html'                                        *      6.52 %       ±5.33% ±7.10%  ±9.28%
path/extname-posix.js n=100000 path='index'                                                    3.09 %       ±3.90% ±5.19%  ±6.78%

Be aware that when doing many comparisons the risk of a false-positive
result increases. In this case, there are 10 comparisons, you can thus
expect the following amount of false-positive results:
  0.50 false positives, when considering a   5% risk acceptance (*, **, ***),
  0.10 false positives, when considering a   1% risk acceptance (**, ***),
  0.01 false positives, when considering a 0.1% risk acceptance (***)                                                                                                                              

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.33%. Comparing base (4e68b54) to head (6fb659b).
Report is 172 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #54546   +/-   ##
=======================================
  Coverage   87.33%   87.33%           
=======================================
  Files         649      649           
  Lines      182602   182602           
  Branches    35035    35037    +2     
=======================================
+ Hits       159469   159475    +6     
+ Misses      16403    16397    -6     
  Partials     6730     6730           

Files with missing lines	Coverage Δ
lib/path.js	95.17% <100.00%> (ø)

... and 21 files with indirect coverage changes

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/61429/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/61642/

[RedYetiDev]

• Passing CI
• Approvals

Is this good-to-go? (It may need a benchmark CI tho)

[RedYetiDev]

A benchmark CI is needed for this to land IIRC.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/62159/

[RedYetiDev]

The latest CI passed (wow!) - author ready?

[anonrig]

Benchmark CI: https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/1635/

[nodejs-github-bot]

Landed in 94a457a