Reuse existing task when going to Bubble settings

Previously we created a new task every time the user opened Bubble settings in the manage menu.

This change reuses the existing task, so only one shows in recents.

Fixes: 309884895
Test: Manual
      - Add bubbles from 2 different apps
      - Open bubble A -> menu -> settings
      - Observe Settings app is shown for app A
      - Go home
      - Expand bubble B -> menu -> settings
      - Observe Settings app is shown for app B
      - Go to recents
      - Observe a single task for Settings
Change-Id: I54bd0a50f58f550e95ad2807ba2555db6d2b8aea