Move the permission.xml to /system_ext

As mentioned in b/132780927, we plan to forbid hidden APIs usage in /product partition,
in other word, apps in /product are allowed to use only either public API or system API.
So, this app will be moved to /system_ext, of course, it is not permanent,
they can be moved back to /product if they don't use hidden API anymore.

Bug: 137908189
Test: m
Test: check whether device boots successfully
Change-Id: I623e0dcc1d3bc1a2a69a6cad34ace1f79532654e
Merged-In: I623e0dcc1d3bc1a2a69a6cad34ace1f79532654e