Allow processes that are bound to by a currently foreground app to

start activities from background

Maintain a set of all client UIDs currently bound to a process, by
updating it accordingly when a service is added/removed to a
process, or the connection is added/removed to the process' service.

Test: atest WmTests:ActivityStarterTests
Bug: 128467234
Bug: 123333161 (daydream case)
Bug: 123500216 (google lens case)
Bug: 129000609 (dialer-duo case)
Change-Id: Ied3ffd8357292d2ad25560c87cd69dc100c9e565