### 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 Variant::can_convert((Variant::Type)p_from, (Variant::Type)p_to);
}
static GDExtensionBool gdextension_variant_can_convert_strict(GDExtensionVariantType p_from, GDExtensionVariantType p_to) {
	return Variant::can_convert_strict((Variant::Type)p_from, (Variant::Type)p_to);
}
static GDExtensionVariantFromTypeConstructorFunc gdextension_get_variant_from_type_constructor(GDExtensionVariantType p_type) {
	switch (p_type) {
		case GDEXTENSION_VARIANT_TYPE_BOOL:
			return VariantTypeConstructor<bool>::variant_from_type;
		case GDEXTENSION_VARIANT_TYPE_INT:
			return VariantTypeConstructor<int64_t>::variant_from_type;
		case GDEXTENSION_VARIANT_TYPE_FLOAT:
			return VariantTypeConstructor<double>::variant_from_type;
		case GDEXTENSION_VARIANT_TYPE_STRING:
			return VariantTypeConstructor<String>::variant_from_type;
		case GDEXTENSION_VARIANT_TYPE_VECTOR2:
			return VariantTypeConstructor<Vector2>::variant_from_type;
		case GDEXTENSION_VARIANT_TYPE_VECTOR2I:
			return VariantTypeConstructor<Vector2i>::variant_from_type;
		case GDEXTENSION_VARIANT_TYPE_RECT2:
			return VariantTypeConstructor<Rect2>::variant_from_type;
		case GDEXTENSION_VARIANT_TYPE_RECT2I:
			return VariantTypeConstructor<Rect2i>::variant_from_type;
		case GDEXTENSION_VARIANT_TYPE_VECTOR3:
			return VariantTypeConstructor<Vector3>::variant_from_type;
		case GDEXTENSION_VARIANT_TYPE_VECTOR3I:
			return VariantTypeConstructor<Vector3i>::variant_from_type;
		case GDEXTENSION_VARIANT_TYPE_TRANSFORM2D: