Add new config to combine unavailable and unknown option

Add a new config for device to combine the block options for
"unavailable" and "unknown" callers options.

Test: Manual; verified that toggling the option to combine the unknown
and unavailable options updates the shared prefs for both.
Bug: 249340131

Change-Id: Id4999c1a71a237096edc895b6f5dbd1aa23c3dc5