Expose `LuaFunction::to_callable` to Godot #188

Job	Run time
macos (universal, template_debug)	47s
linux (x86_64, template_debug)	36s
ios (universal, template_debug)	40s
windows (x86_64, template_debug)	1m 48s
macos (universal, template_release)	52s
android (x86_64, template_debug)	1m 36s
ios (universal, template_release)	38s
linux (x86_32, template_debug)	41s
windows (x86_32, template_debug)	51s
android (x86_32, template_debug)	1m 51s
android (arm64, template_debug)	47s
android (arm32, template_debug)	37s
linux (x86_64, template_release)	35s
windows (x86_64, template_release)	1m 4s
android (x86_64, template_release)	42s
linux (x86_32, template_release)	47s
windows (x86_32, template_release)	1m 5s
android (x86_32, template_release)	41s
android (arm64, template_release)	43s
android (arm32, template_release)	42s
Distribute zip	6s
Test Linux	15s
Test Windows	28s
Test macOS	28s
	19m 20s

Provide feedback