Rollup merge of #132979 - onur-ozkan:skip-exact, r=jieyouxu,tgross35

use `--exact` on `--skip` to avoid unintended substring matches

Without the `--exact` flag, using `--skip tests/rustdoc` can unintentionally skip other tests that match as substrings such as `rustdoc-gui`, `rustdoc-js`, etc.

For debugging, run: `./x.py --stage 2 test rustdoc-ui --skip tests/rustdoc` and `./x.py --stage 2 test rustdoc-ui --skip tests/rustdoc -- --exact`

Resolves rust-lang/rust#117721

try-job: x86_64-apple-1

Author: matthiaskrgr