Reduce having task trampoline when starting app Bubbles

The task trampoline on bubble may unexpectedly happen due to
the following two reasons:
- In commit a8a63db6, the bubble task cannot be reused. Therefore,
  the next activity will be launched in a new Task when needed.
- The bubble task is started as a document task. Since the document
  task cannot be reused, the next activity will be launched in a
  new Task when needed.

Avoid starting app bubble as document task. Also make the app
bubble task reusable just like other normal app tasks.

Bug: 378786164
Test: verified on couple 3p apps.
Flag: com.android.wm.shell.enable_bubble_anything
Change-Id: Ib8e16f3db77aa350f97296f7767b40bd5e966681