Replicas main key rotation implementation

[WildFireFlum]

• Problem Overview
  This PR adds support for main key rotations on demand (for example, when compromised). The implementation uses the replica's consensus key as its main key, thus when an operator sends a consensus key rotation request, the resulting state is that both the main key and the consensus key are changed. The behavior can be reverted back to separate the main key and consensus key (without supporting main key rotations) via the singleSignatureScheme configuration parameter.

• Testing Done
  Unit tests and apollo tests (local and remote)

• Additional Changes Added a convenience directory ${bft-root}/build/apollogs/ which contains links to both the logs of the latest test run and all of the previous test runs. Also added an output file for apollo tests: /concord-bft/build/apollogs/latest/failed_cases.txt which is generated upon failure and contains the names of the tests cases which have failed.