New lint: non-sealed trait added supertrait

[obi1kenobi]

Semver-major, because 3rd party types that used to impl the trait in the last version might not impl the new supertrait imposed in the new version.

Example breaking change in the real-world: https://github.com/awslabs/smithy-rs/pull/2577/files#diff-82252c5a4ad7e9d34be9254db1afe172d0f01c067b121de20ff7f7f29d7cf223L24

[obi1kenobi]

Requires checking whether a trait is sealed, which requires work on the adapter and isn't the best initial onboarding task.

EDIT: This work has been completed, and this lint is ready to be implemented!