### 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
Variant::Type type = (Variant::Type)p_type;
	const StringName method = *reinterpret_cast<const StringName *>(p_method);
	const Variant **args = (const Variant **)p_args;
	Callable::CallError error;
	memnew_placement(r_return, Variant);
	Variant *ret = reinterpret_cast<Variant *>(r_return);
	Variant::call_static(type, method, args, p_argcount, *ret, error);
	if (r_error) {
		r_error->error = (GDExtensionCallErrorType)error.error;
		r_error->argument = error.argument;
		r_error->expected = error.expected;
	}
}
static void gdextension_variant_evaluate(GDExtensionVariantOperator p_op, GDExtensionConstVariantPtr p_a, GDExtensionConstVariantPtr p_b, GDExtensionUninitializedVariantPtr r_return, GDExtensionBool *r_valid) {
	Variant::Operator op = (Variant::Operator)p_op;
	const Variant *a = (const Variant *)p_a;
	const Variant *b = (const Variant *)p_b;
	bool valid;
	memnew_placement(r_return, Variant);
	Variant *ret = reinterpret_cast<Variant *>(r_return);
	Variant::evaluate(op, *a, *b, *ret, valid);
	*r_valid = valid;
}
static void gdextension_variant_set(GDExtensionVariantPtr p_self, GDExtensionConstVariantPtr p_key, GDExtensionConstVariantPtr p_value, GDExtensionBool *r_valid) {