### Godot version

4.2 247c354

### System information

Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1060 (NVIDIA; 30.0.15.1403) - Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz (8 Threads)

### Issue description

#75778 exposed `_validate_property()` to scripting. It's implemented in GDScript and C#, but not GDExtension (depends on #78634).
https://github.com/godotengine/godot/blob/247c3548d810136ffe9c1694cd76db3236efaa90/core/object/script_language_extension.h#L685-L687

Relevant discussion: https://github.com/godotengine/godot/pull/75778#discussion_r1307294940

### Steps to reproduce

1. Add GDExtension script
2. Use `_validate_property()`

### Minimal reproduction project

N/A
return (GDExtensionPtrConstructor)Variant::get_ptr_constructor(Variant::Type(p_type), p_constructor);
}
static GDExtensionPtrDestructor gdextension_variant_get_ptr_destructor(GDExtensionVariantType p_type) {
	return (GDExtensionPtrDestructor)Variant::get_ptr_destructor(Variant::Type(p_type));
}
static void gdextension_variant_construct(GDExtensionVariantType p_type, GDExtensionUninitializedVariantPtr r_base, const GDExtensionConstVariantPtr *p_args, int32_t p_argument_count, GDExtensionCallError *r_error) {
	memnew_placement(r_base, Variant);
	Variant *base = reinterpret_cast<Variant *>(r_base);
	Callable::CallError error;
	Variant::construct(Variant::Type(p_type), *base, (const Variant **)p_args, p_argument_count, error);
	if (r_error) {
		r_error->error = (GDExtensionCallErrorType)(error.error);
		r_error->argument = error.argument;
		r_error->expected = error.expected;
	}
}
static GDExtensionPtrSetter gdextension_variant_get_ptr_setter(GDExtensionVariantType p_type, GDExtensionConstStringNamePtr p_member) {
	const StringName member = *reinterpret_cast<const StringName *>(p_member);
	return (GDExtensionPtrSetter)Variant::get_member_ptr_setter(Variant::Type(p_type), member);
}
static GDExtensionPtrGetter gdextension_variant_get_ptr_getter(GDExtensionVariantType p_type, GDExtensionConstStringNamePtr p_member) {
	const StringName member = *reinterpret_cast<const StringName *>(p_member);
	return (GDExtensionPtrGetter)Variant::get_member_ptr_getter(Variant::Type(p_type), member);
}
static GDExtensionPtrIndexedSetter gdextension_variant_get_ptr_indexed_setter(GDExtensionVariantType p_type) {