Add tools/generate_pyi based on mypy.stubgen POC

[touilleMan]

I think #202 is better suited for our needs, but since I tried this approach it's always nice to keep this code somewhere ;-)

[touilleMan]

note the __doc__ changes in the bindings generation is due to mypy.stubgen having some internal trouble with C extension (python/mypy#7692, basically we need to have a __doc__ field available for each class and each class attribute)

[touilleMan]

the generate godot/binding.pyi looks like this:

from typing import Any

BUTTON_LEFT: int
BUTTON_MASK_LEFT: int
BUTTON_MASK_MIDDLE: int
BUTTON_MASK_RIGHT: int
BUTTON_MASK_XBUTTON1: int

[...]

OS: Any
ProjectSettings: Any
ResourceLoader: Any

[...]

class ARVRInterface(Reference):
    ARVR_AR: Any = ...
    ARVR_EXCESSIVE_MOTION: Any = ...
    ARVR_EXTERNAL: Any = ...
    ARVR_INSUFFICIENT_FEATURES: Any = ...
    ARVR_MONO: Any = ...
    ARVR_NONE: Any = ...
    ARVR_NORMAL_TRACKING: Any = ...
    ARVR_NOT_TRACKING: Any = ...
    ARVR_STEREO: Any = ...
    ARVR_UNKNOWN_TRACKING: Any = ...
    EYE_LEFT: Any = ...
    EYE_MONO: Any = ...
    EYE_RIGHT: Any = ...
    ar_is_anchor_detection_enabled: Any = ...
    interface_is_initialized: Any = ...
    interface_is_primary: Any = ...
    __pyx_vtable__: Any = ...
    @classmethod
    def __init__(self, *args, **kwargs) -> None: ...
    def _from_ptr(self, *args, **kwargs) -> Any: ...
    def get_anchor_detection_is_enabled(self, *args, **kwargs) -> Any: ...
    def get_camera_feed_id(self, *args, **kwargs) -> Any: ...
    def get_capabilities(self, *args, **kwargs) -> Any: ...
    def get_name(self, *args, **kwargs) -> Any: ...
    def get_render_targetsize(self, *args, **kwargs) -> Any: ...
    def get_tracking_status(self, *args, **kwargs) -> Any: ...
    def initialize(self, *args, **kwargs) -> Any: ...
    def is_initialized(self, *args, **kwargs) -> Any: ...
    def is_primary(self, *args, **kwargs) -> Any: ...
    def is_stereo(self, *args, **kwargs) -> Any: ...
    def set_anchor_detection_is_enabled(self, *args, **kwargs) -> Any: ...
    def set_is_initialized(self, *args, **kwargs) -> Any: ...
    def set_is_primary(self, *args, **kwargs) -> Any: ...
    def uninitialize(self, *args, **kwargs) -> Any: ...
    def __hash__(self) -> Any: ...
    def __reduce__(self) -> Any: ...
    def __setstate__(self, state) -> Any: ...

[...]

[touilleMan]

closed now #202 has been merged