Migrate trim_resources_with_background_trim to aconfig flags

Use aconfig to manage this flag and continue rollout.

Bug: 322143614
Bug: 283071711
Test: unit tests
Flag: ACONFIG com.systemui.trimResourcesWithBackgroundTrim DISABLED
Change-Id: Icf665eb60658aaea397d804c5465714065ef1fdd
4 files changed