Action runner cleanup

This ties up the rest of the loose ends with the big ol' Action Runner refactor.

Mainly:

* re-decouples the download/upload/run actions from RunOnecs
* moves these actions out of the runoncehandler directory
* improves the RunOnceHandler's test so it exercises more than just order and type of actions being executed. it can now actually catch bugs in how the actions are constructed (e.g. execute action's actions being performed without a container handle because they were constructed too early)