[Media TTT] Re-name the status bar gesture handler to be more generic.

The next CL will split out the generic swipe-up detection and the
status-bar-specific gesture information, and will add back the class
`SwipeStatusBarAwayGestureHandler`. So, this CL leaves the variable
names to be status-bar-specific.

Bug: 262584940
Test: verify swiping the status bar away when there's an ongoing call
still works
Test: atest OngoingCallControllerTest
Change-Id: Ief581a073ca3809963014405c8233dc13e7e8266

Change-Id: I3da3c306733545df44adfb9518fb4f762f2ace6c