Redefine the Blivet.copy method
    
    Copy-paste the `copy` method of the `Blivet` class, so we can later change it.
    It manipulates with collected installation roots, but these objects are part
    of Anaconda, not Blivet. Blivet should remove this code. Then we can call
    `super().copy()` to create a Blivet copy.
    
    (cherry picked from commit 4a437c330fa624d32f5a23812196fb2fc492765c)
    
    Related: rhbz#2093793