Enable background resource cache trim when device goes idle

The trim implementation was changed from trimMemory(BACKGROUND) to new
trimCaches() implementation which is more appropriate for the context.

See change I32b524ff55d732c0f0879301cc0956ba21e50174 for new
implementation.

Bug: 275486055
Test: atest ResourceTrimmerTest / perfetto profiling on cheetah
Change-Id: Ibd345a5a329ee2b1079fbe82e2bd8d037a476449