pointer input: handle warp events differently from absolute motion events

As Wayland doesn't have a warp event yet, before this commit, warps were dealt with like normal absolute motion events. This trips up games though, which don't deal with actual absolute motion events well. As a solution to that, until an actual warp event is a thing, we send a motion event with a position + a relative motion event with no motion

BUG: 458233 CCBUG: 482476 (cherry picked from commit 630ba5fa)