Allow uid processes in foreground task to start activity in FG

app switch state

Similar to 9d8d5214, a process that has an activity in a
foreground task should also allow to start activity while
in foreground app switch state.

Bug: 208198575
Test: atest BackgroundActivityLaunchTest
Change-Id: Ie04a0aad7a3550abeaa1317e07a6296584972e2c