Use a SupervisorJob in BubbleDataRepository

Using a SupervisorJob ensures that if child coroutines
fail, the scope remains active and we can launch further
coroutines in it.

Also renamed the scope field to exclude io from it. Scopes
should be tied to lifetime of objects, not to dispatchers

Bug: 281083629
Test: Verified that bubbles are still persisted after adding
      new bubbles and reordering them.
Change-Id: I38cc755d5496bfd636d8a4e26f93a26843b0508a