Previously applying the Spotless plugin resulted in a many tasks to be created
per subproject, even for an invocation like `gradle help`.
Using "Task configuration avoidance" APIs means that these tasks will
not be constructed if they will not be required in the task graph.

With this commit, running `./gradlew help -PspotlessModern=true` will no longer
the `spotless`, `spotlessCheck` or `spotlessApply` tasks if they are not
required for task execution. The only remaining task that is eagerly constructed
is "spotlessInternalRegisterDependencies".