Extract unfold classes to a separate library

No behaviour changes in this CL.
Extracted classes related to the fold/unfold
animation (that plays on foldable devices) to
a separate library that does not depend on
system classes. This is necessary to ease
reusing these classes in live wallpapers.

Bug: 231936088
Test: fold/unfold device
Change-Id: Ic1e1ec742867fca9c1209b930accd5738de18e39