Add flag to take view width into account for notification touches

This is primarily to improve usability of landscape accordion shade, where swiping on the scrim (which is most of the screen in that orientation) unexpectedly activates a gesture on notifications instead.

Bug: 335828150
Test: manually verified gestures must be started within bounds of notifs
Flag: ACONFIG com.android.systemui.confine_notification_touch_to_view_width STAGING
Change-Id: I5c3883d487ea437939a06e26562b7c95ddd994ef