Handle promoting app bubbles from overflow

Start a transition to promote an app bubble from overflow. This
allows converting an existing task into a bubble.

Bug: 407475117
Flag: com.android.wm.shell.enable_create_any_bubble
Test: atest BubbleControllerBubbleBarTest
Test: manual
       - create a bubble
       - create a second bubble for e.g. calculator
       - dismiss the calculator bubble so it's in overflow
       - launch calculator from launcher
       - expand bubble bar
       - switch to overflow and tap on the calculator bubble
       - observe calculator task converts to bubble
Change-Id: I4f7bc70e6587160248b251f744b504d224eb5fb8