### Godot version

4.0.2.stable.official.7a0977ce2

### System information

Linux

### Issue description

The following code fails with godot-cpp
```c++
Variant variant_int = 1234;
double double_value = variant_int;
UtilityFunctions::print(double_value); // prints 0. it must be 1234

Variant double_variant = 6789.0;
int int_value = double_variant;
UtilityFunctions::print(int_value); // prints 0. it must be 1234

Variant variant_string = "12345";
StringName string_name = variant_string;
UtilityFunctions::print(string_name); // Segmentation Fault!
```

When godot-cpp converts a `Variant` to another type, it calls `type_from_variant_constructor` without checking its type. It only does  `reinterpret_cast` and does no type conversion.
I think this issue can be solved by implementing type conversion on the godot-cpp side or by making `type_from_variant_constructor` do the type conversion.

### Steps to reproduce

Unzip the minimal reproduction project and run `scons` to build the GDExtension.

### Minimal reproduction project

[variant-conversion-issue.zip](https://github.com/godotengine/godot/files/11171860/variant-conversion-issue.zip)

v->_data._projection = (Projection *)Variant::Pools::_bucket_large.alloc();
		memnew_placement(v->_data._projection, Projection);
		v->type = Variant::PROJECTION;
	}
	_FORCE_INLINE_ static void init_color(Variant *v) {
		memnew_placement(v->_data._mem, Color);
		v->type = Variant::COLOR;
	}
	_FORCE_INLINE_ static void init_string_name(Variant *v) {
		memnew_placement(v->_data._mem, StringName);
		v->type = Variant::STRING_NAME;
	}
	_FORCE_INLINE_ static void init_node_path(Variant *v) {
		memnew_placement(v->_data._mem, NodePath);
		v->type = Variant::NODE_PATH;
	}
	_FORCE_INLINE_ static void init_callable(Variant *v) {
		memnew_placement(v->_data._mem, Callable);
		v->type = Variant::CALLABLE;
	}
	_FORCE_INLINE_ static void init_signal(Variant *v) {
		memnew_placement(v->_data._mem, Signal);
		v->type = Variant::SIGNAL;
	}
	_FORCE_INLINE_ static void init_dictionary(Variant *v) {
		memnew_placement(v->_data._mem, Dictionary);
		v->type = Variant::DICTIONARY;
	}
	_FORCE_INLINE_ static void init_array(Variant *v) {