Feature flag for stopping restricted profiles

Defaults to true by default. Some devices may override this to force the
restricted profile to stop when not in use to save all the memory it
consumes where that is an issue.

There is no framework / first-party code setting it, but since this
is checked every time a user switches into the profile rolling it out
should be relatively straightfoward.

Bug: 71626497
Test: make droid
Change-Id: I7a718c4fdd2d80131df083908129b715d94e824e