Top apps may start fg services even when under bg restriction

We now apply bg restriction policy (appop) on being able to enter a
foreground service lifecycle only when the app is not in a "top" i.e.
directly user-facing state.  This avoids breaking existing supported
lifecycle guarantees involving the order of calls to startService(),
startForeground(), and startForegroundService().  Briefly:  there is a
designed behavior in the following sequence:

  1. startService(intent);
  2. startForeground() on that service; then
  3. startForegroundService(intent)

The intentional behavior is that after step 3, the app is not required
to call startForeground() *again,* redundantly; because that service is
already in a fg lifecycle.

However, new-in-Q code broke this pattern in the case where the user had
imposed bg service restrictions on the app.  For this and for
semantic/model reasons, we now do not apply fg service start
restrictions to the user-facing app, even if the at app is under bg
execution restrictions.  The app is not background at that time, so
should not be expected to face a different execution environment.

Bug: 130048629
Test: Foreground use of GPM under bg restrictions
Change-Id: I0e8c308ac26211082a90c165a64d66b31ab804df