Add permission for MANAGE_EXTERNAL_STORAGE AppOp

Add new MANAGE_EXTERNAL_STORAGE permission. Couple it with
OP_MANAGE_EXTERNAL_STORAGE. Protection level for the permission is
currently signature|appop but will probably change later to |preinstalled.

Bug: 146425146
Test: device boots
Test: atest CtsPermission2TestCases:android.permission2.cts
            .RuntimePermissionProperties#allAppOpPermissionNeedAnAppOp
Change-Id: I0298ca0f6f463c88b95da6ba9853d061c6983da2