The events switch code is largely vestigal and is responsible for
wiring between the consensus state machine and the consensus
reactor. While there might have been a need, historicallly to managed
these subscriptions at runtime, it's nolonger used: subscriptions are
registered during startup, and then the switch shuts down at at the
end.
Eventually the EventSwitch should be replaced by a much smaller
implementation of an eventloop in the consensus state machine, but
cutting down on the scope of the event switch will help clarify the
requirements from the consensus side.