Don't restart processes that host visible activities

We chose to restart processes of background activities that can't handle
the new configuration changes, but the process may also host foreground
activities and by restarting the process foreground activities may also
be interrupted. Therefore we should skip restarting the process that has
visible activities as well.

Bug: 208266661
Test: atest SizeCompatTests#testResetNonVisibleActivity
Change-Id: Ifc50999ffad5640be3c6e34062786f2cc1ebf8b5