[Tracking Issue] Performance improvements in consensus implementation

[cason]

The consensus implementation has a number of performance bottlenecks, mostly related to the extensive use of locks and Go routines. This issue tracks identified bottlenecks and discusses possible generic solutions.

• Find strategy to remove blockID marshalling from most addVote calls #2848
• Increase the Priority weight for Vote and BlockPart channels #2955
• consensus: check votes signatures in parallel, not holding the consensus state mutex #2927
• consensus: change gossip routines sleep and signaling setup #3007
• Speedup WAL encoding #3118
• Don't re-use the internal message queue in block proposal #3130
• Change broadcastHasVote and broadcastHasBlockpart to use TrySend not Send #3151
• Make late votes not enter consensus peer msg queue #3154
• Make late block parts not enter consensus peer message queue #3158
• perf(consensus): Run broadcast routines out of process #3180
• Make gossip routines use TrySend, not Send #3186
• Nodes fail to catch-up in consensus in networks with short block times #3340
• chore(ticker): Prevent ticker from blocking #3317