try to be safer when typing in X: slower, more checks
    
    Summary:
    the main thing this does is try and type slower in X - this
    should cover nearly everywhere we type anything in X, and make
    it type slower. We also add a bit more safety checking to some
    old tests which didn't have it (mainly _do_install_and_reboot)
    - wait_still_screen after typing to make sure all the keypresses
    were registered before continuing.
    
    This is an attempt to mitigate the problems we've seen where
    the wrong text gets typed into the wrong places and the tests
    break.
    
    This branch is live on staging atm. It still has *some* issues,
    but I do think it's an improvement.
    
    Test Plan:
    run the tests (probably several times), compare to
    runs without the change, see if it's better or worse...
    
    Reviewers: jskladan, garretraziel
    
    Reviewed By: garretraziel
    
    Subscribers: tflink
    
    Differential Revision: https://phab.qadevel.cloud.fedoraproject.org/D993