Fix issue of indication area over top of customize lockscreen button

This mostly adds back the xml that was removed here: https://googleplex-android-review.git.corp.google.com/c/platform/frameworks/base/+/24265928/4/packages/SystemUI/res/layout/keyguard_bottom_area.xml

See bug for detailed findings

Currently the indication area and customize lockscreen button belong to 2 different parents, which causes difficulties in z-ordering related to the shortcuts touchability and the customization button touchability.

Once the MIGRATE_SPLIT_KEYGUARD_BOTTOM_AREA flag is relased and removed, this added xml will be removed.

Fixes: 295045628
Test: manual - with no default flags
Test: manual - with split keyguard flag enabled
Change-Id: Ia6a20fe779a712e0b175f677c2b9be34584dcffa