`DrmDevice` and `UdevBackend` now do not need to be wrapped into `StateToken`s anymore, but can return a separate `SessionObserver` object using the new `AsSessionObserver` trait.
This change was motivated by allowing the `UdevHandle` to obtain a mutable reference to an `EventLoopHandle` to create wayland object, e.g. a `wl_output` object.
Previously this was not possible.
Depends on https://github.com/Smithay/wayland-rs/pull/164
- Decouple DrmBackend and DrmDevice through Weak references
- Move EGL-WlBuffer related functionality into it's own trait
- Impl new trait by every struct that can theoretically bind the display although it is no rendering target (no EGLGraphicsBackend), e.g. DrmDevice
- Move texture binding into own struct `EGLDisplay` created by `bind_wl_display` that can be passed around freely
- Add device num to DrmDevice for HashMap storage
- Fixup and enable acceleration on drm and udev examples made possible by the previous changes.