Keep app in high memory adjust if moving from TOP to FGS

If an app was in the TOP state and immediately moved
to a foreground service state, then try harder to keep it
in memory for another 20 seconds before releasing the
memory to bound foreground services. Using an oom_adj value
of 50 which is between "fore" and "vis". So BFGS apps might
get killed ("vis") before this recently FGS'ed app. That
way any app that has a lot of state in memory that it needs
to persist before getting killed has a chance to do so.

Also bind NotificationListeners with a special bind flag
to rank them below FGS (perceptible adj) so that they
can be killed before any other foreground services or
bound services get killed.

Bug: 110969183
Test: Manual for now. Take a bunch of portrait
      pictures and hit home, while being under memory
      pressure with a bunch of notification listeners.
Change-Id: Ie8934c2331afe6450c582b209869aeca7272f58a
Merged-In: Ie8934c2331afe6450c582b209869aeca7272f58a