feat(core-api): getConsensusAlgorithm() on connector API

[petermetz]

Is your feature request related to a problem? Please describe.

We need a way for the ledger connector plugins to be queried at runtime for the consensus algorithm they use.
This is not very meaningful for ledgers that are fixed on a single algorithm, but can be a must have for the ones that support multiple types and have it configurable.

Describe the solution you'd like

For one-trick pony ledgers we can just do it like this:

export enum ConsensusAlgorithm {
  IBFT2_0,
  POW,
  POS,
  etc...
}

public async getConsensusAlgorithm(): Promise<ConsensusAlgorithm> {
    rerturn ConsensusAlgorithm.PROOF_OF_WORK;
}

If the ledger itself provides APIs to query this, then we can just call that, otherwise we may need to have the operator of Cactus specify this in the consortium definition or at least the connector plugin's own configuration somehow.

public async getConsensusAlgorithm(): Promise<ConsensusAlgorithm> {
    const consensusAlgorithm = ... // query ledger at runtime for the algorithm being used
    // maybe have caching introduced here as well? 
    // Not sure because then we would have to deal with cache invalidation...    
    return consensusAlgorithm;
}

Describe alternatives you've considered

Nothing, I'm pretty confident that we need this feature for the higher level, cross ledger transaction coordination protocol that doesn't exist yet, but is definitely coming.

Additional context

This should power the higher level API method proposed here:
#354

cc: @takeutak @sfuji822 @jonathan-m-hamilton