* New syntax is type safe.
* New syntax allows for type safe virtuals in native extensions.
* New syntax permits extremely fast calling.
Note: Everything was replaced where possible except for `_gui_input` `_input` and `_unhandled_input`.
These will require API rework on a separate PR as they work different than the rest of the functions.
Added a new method flag METHOD_FLAG_OBJECT_CORE, used internally. Allows to not dump the core virtuals like `_notification` to the json API, since each language will implement those as it is best fits.
For the time being we don't support writing a description for those, preferring
having all details in the method's description.
Using self-closing tags saves half the lines, and prevents contributors from
thinking that they should write the argument or return documentation there.
We already removed it from the online docs with #35132.
Currently it can only be "Built-In Types" (Variant types) or "Core"
(everything else), which is of limited use.
We might also want to consider dropping it from `ClassDB` altogether
in Godot 4.0.
