Update logic around reusing bubbled activities

This change updates ActivityStarter logic to check the
getLaunchedFromBubble bit and determine whether to allow
inserting new activities into existing bubbled activities.

See go/reuse-bubbled-tasks-wm.

Fixes: 328229865
Test: atest ActivityStarter
Test: atest TaskFragmentTest
Test: atest RootWindowContainerTests
Test: manual
      - Create bubble for conversation A
      - Push a notification for conversation B
      - Tap on notification
      - Observe activity is launched in a new task
Change-Id: I4e240ddb6d2abe3afb685892b4e6ceda5615ade8