DAQModule::register_command should support argument-free transitions in v5

[jcfreeman2]

There are many transition functions in our v5 codebase which have to take an argument data_t (an alias for nlohmann::json) in order to compile. However, this argument isn't used since the transitions are configured via an OKS object kept as member data in the DAQ module class. For v5 we should overload - or replace? - DAQModule::register_command - so that it takes argument-free transition functions.

[jcfreeman2]

Closing this Issue since:
(1) there will still be commands which will need to take in info via a data_t argument, and
(2) it's not just a matter of overloading register_command thanks to CommandMap_t