Replace filetime with std::fs timestamp APIs

[wtcpython]

Replaces the filetime crate with std::fs::set_times and std::fs::set_times_nofollow.

Rust 1.99 is currently beta, so RUSTC_BOOTSTRAP and the feature gate are
temporary and can be removed once 1.99 is stable.

All relevant tests pass.

Fixes #13808

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/rm/isatty (fails in this run but passes in the 'main' branch)
Note: The gnu test tests/seq/seq-epipe is now being skipped but was previously passing.

[oech3]

I strongly disagree with adding such hack. (Maybe, breaking crate.io). If you need nightly API to remove the dep, you are probably using incorrect API.

[oech3]

See caution on config.toml.

[oech3]

The method .set_times for File should work with stable Rust.

[oech3]

We can open dest as File with NOFOLLOW and use method on unix. I don't know any alt for Windows and wasi (or copy code from nightly std to uucore).

[xtqqczze]

Is it necessary to bump rust-version to 1.94.1?

[oech3]

Would you split PR for tests/* unrelated with nightly API?