workspacesView: Support touch/touchpad gestures to switch workspaces

Now that the existing touch/touchpad gestures in windowManager only
handle normal mode, add corresponding gestures for the overview and
hook them up to the existing workspace scroll animations.

#516
4 jobs for !468 with wip/fmuellner/ws-gesture-animations in 6 minutes and 51 seconds (queued for 1 second)
detached
Status Job ID Name Coverage
  Review
passed #250690
check_commit_log

00:02:16

 
  Build
passed #250691
build

00:02:33

 
  Test
passed #250692
test

00:02:01

passed #250693
test-pot

00:02:01