Move AVB related properties from 'system_other' to 'system'

The original CL in AOSP is for 'system' partition.
Howerver, after automerger merges the CL from aosp to goog gerrit, it
patches part of the properties to 'system_other' partition. Correct this by
moving the system_avb* properties to 'system'.

Bug: 31264226
Test: build aosp_angler-userdebug successfully
Change-Id: I1a7128d29c1152315e9b50cfe5bbe13b47b131a7