Before this change, every test rule had an implicit dependency on `@bazel_tools//tools/test:coverage_report_generator`, even though this tool is only used when collecting coverage.

This is fixed by moving it to `CoverageOptions` and using the late-bound default resolver to only create a dependency if coverage is enabled.

Also adds `CoverageOptions` to the set of options classes trimmed by `--trim_test_configuration` so that, as before, changing `--coverage_report_generator` doesn't cause non-test rules to be reanalyzed. This behavior now extends to `--coverage_output_generator`.

Fixes #15088

Closes #16995.

PiperOrigin-RevId: 498949871
Change-Id: I2440fae2655bbb701e918ee2aa7acb008d8f97ed