Auto-grant background execution and data access

Companion apps can declare they want background access and
background execution exceptions via dedicated permissions
in their manifest. If such a permission is requested we
auto-grant the corresponding exception after the user has
chosen a device from the companion UI. These permissions
are appop ones allowing us to use the app ops for gauging
whether the user has made a change after we auto-granted
the permission since we would like to revoke these special
privileges when the app disassociates itself from the
companion device if the user did not make an excplicit
choice otherwise.

While at this auto-grant fixed location permission to the
companion device discovery service.

Test: manual

Change-Id: I46ee4291e5e5a8f7613f0dd75eb61d6b9341f306