Migrate UI tests to `ui-test` crate

[jswrenn]

The ui-test crate allows for annotating the tests themselves with the expected error message. This will make changes to zerocopy or its tests that alter error messages easier to review, as the .stderr file can be merely skimmed.

This PR is marked as a draft, pending the resolution of a ui-test bug that causes it to fail to resolve zerocopy when zerocopy's version is a pre-release.

[oli-obk]

I am unable to reproduce the pre-release failure with either the pinned nightly or the pinned stable. I'm guessing there was some update that wasn't tracked (Cargo.lock is not committed, so I can't tell).