Rewrite CommandLine and FileEnumerator tests using `gtest` test suites

This CL rewrites unit tests for
`CommandLine::QuoteForCommandLineToArgvW` and `FileEnumerator::ForEach`
using the `gtest` test suites.

This is being done instead of the prior hand coding test case loops.

Bug: 1470370
Change-Id: I46eacafb5f128149c50c23e561e4d854d0f18179
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4753760


Reviewed-by: Lei Zhang <thestig@chromium.org>
Code-Coverage: Findit <findit-for-me@appspot.gserviceaccount.com>
Auto-Submit: S Ganesh <ganesh@chromium.org>
Commit-Queue: S Ganesh <ganesh@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1180443}