Port `clone.py` logic into `translate.cc`

[knikolla]

Currently there is a Python script called clone.py that clones an LSVD image. This script reimplements the LSVD data structures and is at risk of falling out of date.

Implementing this as part of the C++ codebase would allow it to use the data structures directly.

translate.cc is used by imgtool which is used to perform LSVD image manipulation.

lsvd-rbd/translate.cc

Line 1575 in 3c04f8d

int translate_clone_image(sptr<backend> objstore, const char *source,