Only stabilize tasks during quick switch session

- A stabilization session starts when going to a new task via a quick switch
- A stabilization session ends after 5 seconds on the same task or when completing
  a gesture to go to home or overview
- We track the system task order and copy it for the duration of the stabilization session
- After the session ends, we switch back to the system task order
- Remove ENABLE_TASK_STABILIZATION flag (and also QUICK_SWITCH)

Bug: 111926330
Change-Id: I2c18dff2d20ad02b73a4935ac534e9fc9f5f49c0