Lint rule to warn on Configurations

Configurations need to implement correct equals and hashCode, as they're used in map keys under the hood. Configurations that are neither kotlin `object` nor `data class` but simply `class` pose a risk if they don't implement those.

Locate the repository's existing lint-rule entry points and tests, then inspect how Kotlin classes are identified. Define the warning for configurations that are plain classes without equals and hashCode, and confirm the test suite covers object, data class, and ordinary class cases.

Written by the indexing model from the issue text.