Mark bubbles as updated when they're added to the stack

If you add a bubble via the button on the notification but
if the notif for it is older than the notifs for the bubbles
in the stack, then that added bubble is removed immediately.

This isn't expected and can result in the view state being
out of sync with bubble data, i.e. BubbleStackView contains
the view but BubbleData doesn't have the bubble so it can
get added again (but the view is already in BSV causing the
crash).

This fixes the issue by marking newly added bubbles as
"updated" which will ensure the newly added bubble won't
be immediately removed.

Had to adjust the tests to be setting a current time since
that's what's used to mark the update time.

Test: atest BubbleDataTest
Bug: 207083906
Change-Id: I425de9c1ca514066340f9123b6004820e98674fd