Godot's VariantUtilityFunctions is named UtilityFunctions in godot-cpp

### Godot version

4.4.stable

### godot-cpp version

4d8c05f405929480ef2eed7300447c4647da2d6f

### System information

macOS 14.6.1

### Issue description

There is a mismatch between the name of the utility functions struct/class in core vs in godot-cpp.

In the core engine:

```cpp
struct VariantUtilityFunctions {
// Math
```

In godot-cpp:

```cpp
namespace godot {

class UtilityFunctions {
public:
```

We should rename one or the other to allow C++ code to work for both.

In the meantime, it's easy to work around: https://github.com/godot-dimensions/godot-4d/commit/b28c83d2608191e8187703efbbeeee16365975e4

### Steps to reproduce

N/A

### Minimal reproduction project

N/A