More flexible API enforcement policy.

This CL adds the basics to set black, dark gray or light gray list
enforcement, rather than just black as before. It's not possible to
actually set the policy per-package yet.

PackageDexOptimizer still uses a single bit, for API checks on/off, rather
than the new enum. It assumes blacklist enforcement internally. This can
be improved in a follow up CL.

(cherry-picked from commit e52130ae)

Test: m
Test: Boot device

BUG: 73337509
Change-Id: Ieb4bd9cc439c6a5b8fb9424d8902d8b46aec309f
Merged-In: Idd73c9938592c5c4d67cfb9efefdffed0dd5f262