Changes the `<godot/gdextension_interface.h>` include to simply
`<gdextension_interface.h>`.
Refactor and better document the SCons and CMake logic around setting
the paths to the header and API JSON file.
Non-exhaustive list of case-sensitive renames:
GDExtension -> GDNative
GDNATIVE -> GDEXTENSION
gdextension -> gdnative
ExtensionExtension -> Extension (for where there was GDNativeExtension)
EXTENSION_EXTENSION -> EXTENSION (for where there was GDNATIVE_EXTENSION)
gdnlib -> gdextension
gdn_interface -> gde_interface
gdni -> gde_interface
The returned value "ret" may be nullptr in which case the code would crash because "object_get_instance_binding" can't be called on nullptr input.
This should be very easy to reproduce, I encountered it pretty much any time I called a method that returned Ref<Something>. E.g.:
Ref<GeometryInstance3D> instance;
instance.instantiate();
instance.get_mesh(); // Crash because no mesh was set for the instance and the returned value was nullptr.