Fix two activity stack leak cases

1) An activity stack was created while starting an activity. The stack
should be destroyed if activity did not landed on the stack eventually.

2) Recent stack shouldn't be created if the recents component is also
the home activity, while showing Recents in split-screen.

Bug: 137232340
Test: atest ActivityStarterTests ActivityVisibilityTests

Change-Id: Id870bc5249cd98b891ee7e6a1968f1ee2c6060fd