Add periodic trace of GSM state

[nfrisby]

@karknu found a misbehavior with a small docker-compose testnet, and asked Consensus to dig in. If the node had been reporting its GSM state with some frequency automatically, then it would have taken us 5 minutes to create our feedback instead of a few hours (since we struggled to understand the docker-compose configuration mechanisms).

This Issue is to add two tracers to the GSM:

• trace the initial GSM state on start up
• every 10s or so, trace the current GSM state

These seem small enough to be in the node enabled by default --- at least in ConsensusNode: GenesisMode.