[repository] move task manager instantiation outside repository. Repository callers are in charge of providing a task manager. The task manager is optional when the repository is not a server. This part is not really expected to work well yet. But we aim to remove all task management responsibilities from the Repository object.

[repository] split repo initialization from starting looping task (closes #2204047) This separation highlights that two distinct operations are done. This is a step towards a full distinction between repo, server and looping tasks