This commit refactors some of the rpc-related functions in the
Blockchain class to be more composable. This change was made
in order to make implementing the new zmq rpc easier without
trampling on the old rpc.
New functions:
Blockchain::get_num_mature_outputs
Blockchain::get_random_outputs
Blockchain::get_output_key
Blockchain::get_output_key_mask_unlocked
Blockchain::find_blockchain_supplement (overload)
functions which previously had this functionality inline now call these
functions as necessary.
Thomas Winget