IF: Miscellaneous code cleanups

[greg7mdp]

I'd like to do a code cleanup pass when the HS files are not actively modified by many people. For example.

• avoid excessive vector copies when aggregating/verifying signatures (include update fc & bls12 submodule to use std::span instead of std::vector for input parameters.
• reduce number of calls to fc::crypto::blslib::aggregate when verifying a quorum_certificate (see evaluate_quorum)
• update hotstuff.hpp class structure to the new version documented by Areg in IF: Redefine view number and add generation number to the finalizer set #1589
• add simpler type aliases in hotstuff.hpp to make the code less verbose, for ex:

   using bls_public_key_t  = fc::crypto::blslib::bls_public_key;
   using bls_private_key_t = fc::crypto::blslib::bls_private_key;
   using bls_signature_t   = fc::crypto::blslib::bls_signature;
   using bls_key_map_t     = std::map<bls_public_key_t, bls_private_key_t>;

• As discussed with Fabiana, HotStuff should be a standalone Finite State Machine (which can be tested independently and doesn't know about Leap or Controller), which internally maintains the separation pacemaker (liveness) and chain (safety), but imho these classes are tightly coupled and can be friend of each other.
  In addition there should be an interface class connecting Leap and the HotStuff FSM.