Honors three_button_corner_swipe flag.

This allows the corner swipe gesture to be recognized while in 3
button navigation mode.

Demo: https://drive.google.com/file/d/1cwma-K5Ht-CYYmFgHw4OgefCS8Zvp140/view?usp=drive_link&resourcekey=0-rYzpTFc0l8R53QnaLwBANg
 - Corner swipe works
 - Other swipes don't do anything
 - Buttons still behave as expected
 - Long Press Home still invokes Circle to Search

Bug: 361651619
Bug: 356441231
Test: See video
Flag: com.android.systemui.shared.three_button_corner_swipe
Change-Id: I0765868dd1ad9786dc5b5f0574d107221ef13556