Get rid of states that aren't relevant to the UI
See commit messages, it boils down to: Some of the states we had were implementation details.
This will leave some breakage, so a coordinated release between Calls and Phosh is necessary.
This will provide a better separation between application logic and UI by loosening the coupling between (internal) call states and ui call states (these were previously mapped 1:1).
After this gets merged I will document the states in the DBus side in Calls.