Enable new touchpad stack by default

The Gestures library-based stack now has feature parity with the old one
(except for rotation gestures) and so can safely be enabled by default
rather than requiring dogfooders, testers, etc. to change the sysprop
manually.

Bug: 251196347, 264996455
Test: atest inputflinger_tests
Change-Id: Ia1f8e1e6e36bc972d00cd847a64af426b04ae360