test: Migrate to `vitest` with `.unpacked` and Asar Header snapshots

[mmaietta]

Was having a fun chat with @erickzhao and wanted to see if I could lend a hand!

This PR accomplishes a few things:

• Migrates from mocha to vitest
• Converts all test files to typescript 🙌🏻
• Adds a new helper function verifySmartUnpack that I pulled from electron-builder's testing approach
  • It reads the asar header and validates it against the snapshot file
  • Provides a hook for additional asar Filesystem operations/verifications should so be desired
  • "Walks" the unpacked directory and stores a snapshot of the folder/file/symlink hierarchy.

With verifySmartUnpack, the header snapshot allows finer granularity of what is happening under the hood, especially with regards to symlinks and integrity calculations. Example respective snapshots excerpts below:

    "var": {
      "link": "private/var",
      "unpacked": true,
    },

"dir1": {
 "files": {
   "file1.txt": { 
     "integrity": {
       "algorithm": "SHA256",
       "blockSize": 4194304,
       "blocks": [
         "420149d3f852894ba7f32e9d3ec7d8919ee2451724bf2580b0186cd373bd6d82",
       ],
       "hash": "420149d3f852894ba7f32e9d3ec7d8919ee2451724bf2580b0186cd373bd6d82",
     },
     "size": 9,
     "unpacked": true,
   },
 },
}

Then the "walk" snapshot functionality allows all these lines to become just verifySmartUnpack('tmp/packthis-unpack-subdir-cli.asar') https://github.com/electron/asar/blob/121efebd2d02e374713cb513eb56a0e3db9534e9/test/cli-spec.js#L182-L185

Additional Notes:

• vitest required dropping rimraf.sync(...) from the beforeEach hooks since the tests are in parallel and would cause random tests to fail. I've moved the rimraf to the vitest-setup.ts
• Ideally, to retain the previous functionality of beforeEach->rimraf, the tests need to run in isolation (which I wasn't able to achieve with singleThread) OR a random tmp dir is used each time that is unique to each test case. The latter option would require too large of a change and I wanted to keep changes in this PR isolated to the test/ folder as much as possible.
• src/asar.ts file change is required though for options?: ListOptions to match its upstream .listFiles(options) API
• lib required being bumped to es2019 so as to have access to flat() API
• cleaned up package.json devDependencies

Should this PR be accepted w/ verifySmartUnpack approach, the next steps would be cleaning up the test asserts that are now covered by the "walking" snapshots.

[mmaietta]

Whelp, looks like this PR would depend on the upcoming node 22 upgrade. CC @erickzhao

error [email protected]: The engine "node" is incompatible with this module. Expected version "^18.0.0 || ^20.0.0 || >=22.0.0". Got "16.20.1"