Set incremental apk directories

Set up incremental storages such that it works with the new app code
path layout.

Ensures that package names do not show up in /proc/mounts

$ cat /proc/self/mountinfo
2806 90 0:79 / /data/incremental/data_incremental_tmp_1042476774/mount rw,nosuid,nodev,noatime shared:34 - incremental-fs incfs.img rw,read_timeout_ms=10000,readahead=0,rlog_pages=2,rlog_wakeup_cnt=10
6946 90 0:79 /st2 /data/app/~~WE4d9B-MZg0iZckOxIhPGQ== rw,nosuid,nodev,noatime shared:34 - incremental-fs incfs.img rw,read_timeout_ms=10000,readahead=0,rlog_pages=2,rlog_wakeup_cnt=10
7014 2806 0:79 /st2 /data/incremental/data_incremental_tmp_1042476774/mount/st2 rw,nosuid,nodev,noatime shared:34 - incremental-fs incfs.img rw,read_timeout_ms=10000,readahead=0,rlog_pages=2,rlog_wakeup_cnt=10
7013 6946 0:79 /st2 /data/app/~~WE4d9B-MZg0iZckOxIhPGQ== rw,nosuid,nodev,noatime shared:34 - incremental-fs incfs.img rw,read_timeout_ms=10000,readahead=0,rlog_pages=2,rlog_wakeup_cnt=10

BUG: b/147371381 b/148237378
Test: manual
Change-Id: I149903ae63ee27da5957e41c16f21f3435f9e636