Add unit test checking to `cargo check`

Add unit test checking to `cargo check`

- Add `--profile test` flag to `cargo check` that will enable checking of unit tests.
- `--tests` will implicitly enable checking of unit tests within the lib.
- Don't implicitly compile binaries when using just `--test` filters.
- Fix erroneously linking tests when run with `--test`.

Fixes #3431, #4003, #4059, #4330.