* Use objc2
* Replace `objc_id`
* Remove sel_impl import
* Fix `add_method` calls
* Fix accessing raw FFI functions
* Fix Encode impl
* Fix message sends arguments that do not implement `Encode`
* Use immutable reference in a few places where now necessary
See https://github.com/madsmtm/objc2/pull/150 for a bit of background
* Add a few Send + Sync bounds where examples require it
This is something we'll need to look into properly
* Use `&'static Class` instead of `*const Class`
Safer and more ergonomic. Also required for `msg_send_id!` macro
* Use msg_send_id! and rc::Id
* Update objc2 to v0.3.0-beta.2
* Replace `BOOL` with `Bool` when declaring delegates
This makes cacao compile on Aarch64 again
* Remove a few impossible to use correctly `into_inner` functions
These consumed `self`, and hence also dropped `Id` variable that was responsible for keeping the returned pointer alive
* Remove a few impossible to use correctly `From` implementations
* Quickly fix UB with using BACKGROUND_COLOR ivar
* Fix double-freeing of windows
* Fix double freeing of strings
* Fix a few remaining double-frees
