fs: improve `ExistsSync` performance on Windows

[anonrig]

Simplifies code by using std::filesystem. Since std::filesystem is C++17, this pull-request can be backported to 18 and 20.

The following benchmark shows 2% improvement, but I'm sure if we had a Windows benchmark-ci machine it would have better results. Especially for symlinks, we are now not executing 2 different operating-system calls, and only one.

FYI: std::filesystem::exists follows symlinks.

Benchmark code:

const fs = require('node:fs');
const exists = fs.existsSync(__filename);
console.log(exists);

Benchmark result:

PS C:\Users\yagiz\Desktop\coding\node> hyperfine ".\out\Release\node .\exists-bench.js" " .\node-pr .\exists-bench.js" --warmup 10
Benchmark 1: .\out\Release\node .\exists-bench.js
  Time (mean ± σ):      48.8 ms ±   2.9 ms    [User: 2.2 ms, System: 3.3 ms]
  Range (min … max):    41.6 ms …  55.3 ms    56 runs

Benchmark 2:  .\node-pr .\exists-bench.js
  Time (mean ± σ):      47.7 ms ±   2.0 ms    [User: 1.3 ms, System: 2.8 ms]
  Range (min … max):    42.2 ms …  50.5 ms    60 runs

Summary
   .\node-pr .\exists-bench.js ran
    1.02 ± 0.07 times faster than .\out\Release\node .\exists-bench.js

cc @nodejs/fs @nodejs/platform-windows