Rig element names should be case insensitive

The control rig editor should enforce case insensitivity for any names that can be created within the editor.  Currently, it's possible for control names to be created that are the same as existing bone names, except for the case.  When the control rig is later serialized, these differences in case are lost and any clashing name will appear to change when the rig is reloaded.  This can cause other odd behaviours like [Link Removed].

1. Create a control rig
2. Import the UE5 mannequin (this will contain a bone 'clavicle_l'
3. Now create a control and name it 'Clavicle_l'
   1. Expected behaviour: The new control should use the same name as the bone (ie. lower case) since it was registered first
   2. Actual behaviour: The new control name has a different case to the bone name