Increase swipe gesture areas for hub

This change increases the areas on the side of the lockscreen, dream,
and hub that can be used to start a swipe gesture.

The lockscreen swipe area is only increased to 40dp for now, as the
spec of 68dp causes overlap with notifications, which needs to be
resolved with additional touch handling changes.

Bug: 322549765
Test: manually verified on device, see video in bug comment
Flag: ACONFIG com.android.systemui.communal_hub STAGING
Change-Id: Ie5eb9752a577b0dd07fef2d7251c706eccf17f74