Add ANGLE_ENABLED_APP to CoreSettings

The way we were checking Settings was invoking a 2ms hit.

Move ANGLE_ENABLED_APP to CoreSettings, which are already
available to the ActivityThread, eliminating the hit.

Test: Verify developer option works as expected
Test: atest google/perf/app-startup/benchmark-app-hermetic/cold-dropcache-test
Bug: 117107368
Bug: 80239516
Change-Id: I3df4c3c43489a338b3631484a8811b38c4eff2e6