The error handling at the `error:` label tears down the whole state. Thus, the
state needs to be fully initialized in order for the tear down to succeed.
Currently, if e.g. `sd_bus_open_user()` fails, a `segfault` is triggered by
the tear down. This commit adds individual tear down code that only touches
stuff that until that point was successfully initialized.
* Initial session support WIP
Remove libdrm dependency
Remove display from context, add dbus properties
Use random names for shm and pw_stream, init the stream only for new cast instances
Separate cast initialized flag from refcount, cleanup names and comments
* Refactor and stability improvements
Properly report xdp screencast implementation version
