Auto merge of #9892 - ehuss:cargo_test-ignore-reason, r=weihanglo

Auto merge of #9892 - ehuss:cargo_test-ignore-reason, r=weihanglo

Add requirements to cargo_test.

This extends the `#[cargo_test]` attribute to support some additional requirements to control whether or not a test can run. The motivation for this is:

* Can more clearly see when a test is disabled when it prints "ignored"
* Can more easily scan for disabled tests when I do version bumps to see which ones should be enabled on stable (to pass on CI).

The form is a comma separated list of requirements, and if they don't pass the test is ignored.  The requirements can be:

* `nightly` — The test only runs on nightly.
* `>=1.55` — The test only runs on rustc with the given version or newer.
* `requires_git` — Requires the given command to be installed.  Can be things like `requires_rustfmt` or `requires_hg`, etc.

This also enforces that the author must write a reason why it is ignored (for some of the requirements) so that when I look for tests to update, I know why it is disabled.

This also removes the `CARGO_TEST_DISABLE_GIT_CLI` option, which appears to no longer be necessary since we have migrated to GitHub Actions.