Remove @legacy-covers annotations on class metadata - part 2

Problem/Motivation

During the annotation-to-attribute test metadata migration, we converted no longer supported @covers annotations to @legacy-covers.

Proposed resolution

On class level metadata, we can map @legacy-covers to #[CoversClass], #[CoversMethod], #[CoversFunction], #[CoversTrait] attributes.

In this issue target Kernel tests.

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet