## Description

Removes the `flutter_test` dependency on `quiver`, instead using the more targeted `clock` and `fake_async` packages.

## Related Issues

https://github.com/flutter/flutter/issues/53908

## Tests

No changes to tests

## Checklist

Before you create this PR confirm that it meets all requirements listed below by checking the relevant checkboxes (`[x]`). This will ensure a smooth and quick review process.

- [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
- [x] I signed the [CLA].
- [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement].
- [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] All existing and new tests are passing.
- [x] The analyzer (`flutter analyze --flutter-repo`) does not report any problems on my PR.
- [x] I am willing to follow-up on review comments in a timely manner.

## Breaking Change

Did any tests fail when you ran them? Please read [Handling breaking changes].

- [ ] No, no existing tests failed, so this is *not* a breaking change.
- [x] Yes, this is a breaking change. *If not, delete the remainder of this section.*
   - [x] I wrote a design doc: https://docs.google.com/document/d/1EkkLbECNBwHgddBQAZqEy7iQLTIxR1rgChKzxcLwhio/edit
   - [x] I got input from the developer relations team, specifically from: @RedBrogdon
   - [x] I wrote a migration guide:  https://github.com/flutter/website/pull/3932

<!-- Links -->
[issue database]: https://github.com/flutter/flutter/issues
[Contributor Guide]: https://github.com/flutter/flutter/wiki/Tree-hygiene#overview
[Test Coverage]: https://github.com/flutter/flutter/wiki/Test-coverage-for-package%3Aflutter
[Flutter Style Guide]: https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[Features we expect every widget to implement]: https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[Tree Hygiene]: https://github.com/flutter/flutter/wiki/Tree-hygiene
[Handling breaking changes]: https://github.com/flutter/flutter/wiki/Tree-hygiene#handling-breaking-changes