Add a DEBUG flag detector lint rule

This Android Lint rule checks for `DEBUG` field usage that is
either set to true or marked as non-final. Boths scenarios are
generally undesirable in production code, as they both prevent code
optimization and can lead to unintended behavior (e.g., log spam).

Follow-up work will explore migrating this into a more general rule
that can be used outside of the framework and core platform targets.
It will also be upgraded to an `ERROR` after the appropriate lint
baselines have been updated.

Bug: 436095548
Test: presubmit + manual verification
Test: atest AndroidFrameworkLintCheckerTest --host
Flag: EXEMPT Android lint rule addition
Change-Id: I45c5d72a6f20cc6f32361c7ce4050e84fc401dd0