Add Clone trait to auth-related structures

[alexeykoren]

Add Clone trait to auth-related structures

[what-the-diff]

PR Summary

• Enhanced Flexibility of SpendAuth type in InProgressSignatures trait
  The SpendAuth type in InProgressSignatures trait has been updated to incorporate the Clone trait bound. This means it can now create a copy of an object that uses this type.

• Improved Cloning ability of SpendAuth in Authorization trait
  The SpendAuth type in Authorization trait has also been upgraded with the Clone trait bound, bringing in the capability to duplicate objects of this type.

• Added Cloning Capability for MaybeSigned enum
  The MaybeSigned enum has been enriched with the Clone derive. This adds the ability for objects of this type to create exact copies of themselves.