Add oom_adj_score tier for cached apps with UI

The oom_adj_score for freezer-eligible apps that recently entered cached
has been bumped to 920 (from 910). The 910-914 range is now assigned to
the 5 most-recently-cached apps that have shown any UI.

Test: - Test logs to verify that apps opened in succession are
        sequentially assigned 910-914 oom scores.
      - atest MockingOomAdjusterTests (with each combination of
	ENABLE_NEW_OOMADJ and USE_TIERED_CACHED_ADJ)
Flag: EXEMPT USE_TIERED_CACHED_ADJ is disabled by default; any change
      that results in this path actually being used will be flag-guarded
Bug: 345743959
Change-Id: I7130e12bdf099b69c69d044a62ff66f71030d3ca
2 files changed