Add LockedAxes

[Jondolf]

Adds a LockedAxes component for locking translational and rotational axes.

The locked axes are represented as a u8, where each axis has one bit, a total of 6 bits. There are methods like lock_translation_x, lock_rotation_y and unlock_rotation_z, and the constants TRANSLATION_LOCKED, ROTATION_LOCKED and ALL_LOCKED.

To take the locked axes into account, an effective mass/inertia is computed before applying any positional or rotational updates. For example the effective mass is just a vector where the locked axes have a mass of zero. This works similarly for other updates.

Example

use bevy::prelude::*;
use bevy_xpbd_3d::prelude::*;

fn spawn(mut commands: Commands) {
    // Spawn a capsule that only rotates around the Y axis
    commands.spawn((
        RigidBody::Dynamic,
        Collider::capsule(1.0, 0.5),
        // In 2D, use use LockedAxes::new().lock_rotation()
        LockedAxes::new().lock_rotation_x().lock_rotation_z(),
    ));
}