Backup lockscreen widgets on mobile

This change allows lockscreen widgets to be backed up on mobile by
checking the new flag and config in addition to the config used on
tablets.

Fix: 395239759
Test: verified widgets are backed up and restored on a felix; there are
no exiting unit test for the system ui backup helper
Flag: com.android.systemui.glanceable_hub_v2

Change-Id: I2083d9e7667c4cb4d33a3a149234c25353e47fa8