Adjust back gesture exclusion areas on glanceable hub.

This changelist accounts for layout direction when setting insets for
excluding back gesture on the glanceable hub.

Test: atest GlanceableHubContainerControllerTest#gestureExclusionZone_setAfterInit_rtl
Test: atest GlanceableHubContainerControllerTest#gestureExclusionZone_setAfterInit_backGestureEnabled_rtl
Bug: 320786721
Flag: com.android.systemui.glanceable_hub_back_gesture

Change-Id: I12814d075aeebe9a362900f6e44e9a4a18ee821b