Reporters now driven from messagebus

[StephenWattam]

So, the reporters are very similar in structure but now they only respond to events.

Reporters subscribe to events on instantiation, same as the rest of the components. They're instantiated in the same place as before, though there is no longer any need for this to be the case.

There's a huge problem with repeating phases right now where the bus never forgets things, and it becomes possible to insert them in the wrong order. This is fixable and fixing it requires rethinking the less-than-ideal phases system.

This PR is kinda unsatisfying. It makes the change it claims but I feel like everything is quite fragile and it hasn't solved any problems in the codebase :-/

[github-actions[bot]]

_{Autogenerated by pr-status-giphy-action.}