Restrict background activity start by task

We now also allow apps to start activity in its own background task, while
that task won't move to front.

Background activity is not allowed to be started in new task or app
is not in that task stack.
Also, task moving / reparent task is not allowed.

Bug: 128772406
Test: atest android.server.wm.BackgroundActivityLaunchTest
Change-Id: I20f501e755f30f9ef581f7f8c39a2875f959e5b8