### 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)

class VariantInternal {
	friend class Variant;
public:
	
	_FORCE_INLINE_ static void initialize(Variant *v, Variant::Type p_type) {
		v->clear();
		v->type = p_type;
		switch (p_type) {
			case Variant::STRING:
				init_string(v);
				break;
			case Variant::TRANSFORM2D:
				init_transform2d(v);
				break;
			case Variant::AABB:
				init_aabb(v);
				break;
			case Variant::BASIS:
				init_basis(v);
				break;
			case Variant::TRANSFORM3D:
				init_transform3d(v);
				break;
			case Variant::PROJECTION:
				init_projection(v);
				break;