VehicleWheel3D: rotation does not match actual movement

### Tested versions

Godot: v4.4.1.stable.steam [49a5bc7b6]

### System information

Windows 11, Forward+

### Issue description

VehicleWheel3D, while capable to tract the vehicle in any direction (where it is pointing), rotates only along the Z axis. For example, if the wheels are pointing into +X direction, they are not rotating, unless the vehicles starts to shift along the Z axis. This also relates to `get_rpm` method of the wheel.

### Steps to reproduce

1) Create a simple vehicle using VehicleBody3D and 4 VehicleWheel3D's, but where the front of the car is at +X, for example. And wheels pointing the same way.
2) Add non-circular meshes (like boxes) to wheels to better see the rotation.
3) Drive the car. While moving forward, wheels are not rotating. Nor visually, nor logically (get_rpm is virtually zero).
4) Steer the car, so that the car (and the wheels themselvs) get some velocity along the Z axis relative to the car itself.
5) You see that wheels starts to rotate according to their Z-compound of the velocity.

### Minimal reproduction project (MRP)

[car-wheels.zip](https://github.com/user-attachments/files/21477003/car-wheels.zip)

Start with the VehicleWheel3D behavior described in the issue and reproduce it using the linked car-wheels.zip project, focusing on wheel rotation and get_rpm when the vehicle faces +X. Compare forward movement with movement along Z and verify that both the visible rotation and reported RPM follow the wheel's actual travel direction.

Written by the indexing model from the issue text.