A0-4152: Global consensus threshold and other crypto improvements

[timorleph]

Small, seemingly disjointed changes to the crypto API and some resulting changes in the consensus unit tests. They were easy to split off of the bigger refactor so I did that to make that one smaller and make it clearer what the version changes entail.

[github-actions]

Please make sure the following happened

• Appropriate tests created
• Infrastructure updated accordingly
• Updated existing documentation
• New documentation created
• Version bumped if breaking changes

[kostekIV]

What about:

• function quorum in mock/src/crypto/keychain.rs
• function quorum in crypto/src/signature.rs
• in crashed_nodes_recover fn on line 168 in fule consensus/src/testing/crash_recovery.rs you can also use consensus_threshold function