Change "Toolbox" references to "Toolbx"
    
    See https://debarshiray.wordpress.com/2021/11/10/toolbox-is-now-toolbx/
    
    Language here attempts to mirror CoreOS docs:
    
    * "A toolbox" is unchanged
    * References to the `toolbox` binary are unchanged (or clarified)
    * "Toolbox container" is changed to "Toolbx container"
    * The name of the project itself is changed