* fix DiffKVStores(), store/types gets 100% coverage
DiffKVStores() used to return duplicated entries
in some cases.
Add test cases, aiming to reach 100% coverage for
store package.
Remove duplicate Cp function from the store package.
Same functionality is provided by types.CopyBytes().
* More test cases
Co-authored-by: Alexander Bezobchuk <alexanderbez@users.noreply.github.com>
Alessio Treglia