Add patrol tests

[piotruela]

This PR add testing 2 packages that are part of the Patrol testing tool:

• patrol_cli
• patrol
• patrol_finders

They relies on multiple dependencies pinned by the Flutter SDK, most heavily on the flutter_test API.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read the Flutter Style Guide recently, and have followed its advice.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

[kevmoo]

Uh... @devoncarew ? @natebosch ?

[devoncarew]

I'm curious - how much of package:test_api is used? I believe that's currently very lightly used, and mostly by flutter test. Adding a test here for a package that uses it might effect our ability to evolve that api.

[natebosch]

It seems like this is primarily a version-change detection test for the test_api package? I don't think we have made, nor should yet make, any promises about not bumping to a new major version of test_api.

I do think that as we iterate further on the extensibility of the test runner, package:test_api will likely become a dependency in more places.

[piotruela]

@devoncarew @natebosch I get your point. I removed from the tests the package that directly depends on test_api and updated PR description.