[Migration] Restore tests that use package:linter

[scheglov]

We use actual package:linter to verify that package:linter can generate lints, enable or disable them, change severity, etc. But with package:analyzer migrated, including its tests, we cannot import package:linter until it is migrated as well.

For now I will:

1. Comment out imports of package:linter and registerLintRules() invocations.
2. Mark corresponding tests as failing.

[srawlins]

@scheglov do you know if this was finished?