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fs: move getValidMode to c++ for better performance

Rodrigo Muino Tomonari requested to merge github/fork/andremralves/getValidMode-to-cpp into main 
                                                     confidence improvement accuracy (*)    (**)   (***)
fs/bench-copyFileSync.js n=10000 type='invalid mode'        ***     69.61 %      ±10.49% ±14.01% ±18.33%
fs/bench-copyFileSync.js n=10000 type='invalid path'                 1.58 %       ±6.12%  ±8.14% ±10.59%
fs/bench-copyFileSync.js n=10000 type='valid'                        1.90 %      ±10.90% ±14.50% ±18.88%

Be aware that when doing many comparisons the risk of a false-positive result increases.
In this case, there are 3 comparisons, you can thus expect the following amount of false-positive results:
  0.15 false positives, when considering a   5% risk acceptance (*, **, ***),
  0.03 false positives, when considering a   1% risk acceptance (**, ***),
  0.00 false positives, when considering a 0.1% risk acceptance (***)
                                                         confidence improvement accuracy (*)    (**)   (***)
fs/bench-accessSync.js n=100000 type='existing'                         -2.88 %       ±6.17%  ±8.22% ±10.72%
fs/bench-accessSync.js n=100000 type='invalid-mode'             ***     52.14 %      ±10.53% ±14.03% ±18.30%
fs/bench-accessSync.js n=100000 type='non-existing'                     -0.87 %       ±5.86%  ±7.80% ±10.17%
fs/bench-accessSync.js n=100000 type='non-flat-existing'                 0.83 %       ±6.60%  ±8.78% ±11.43%

Be aware that when doing many comparisons the risk of a false-positive result increases.
In this case, there are 4 comparisons, you can thus expect the following amount of false-positive results:
  0.20 false positives, when considering a   5% risk acceptance (*, **, ***),
  0.04 false positives, when considering a   1% risk acceptance (**, ***),
  0.00 false positives, when considering a 0.1% risk acceptance (***)

Ref: https://github.com/nodejs/performance/issues/111

The improvements are noticeable for cases where an error related to mode is thrown.

Thanks to @anonrig for the idea.

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