Refoctor AriesAgentController

* correct linting
* remove optional args and initialise all controllers by default
* Outsource webhook handling
* create a AriesMultitenantController child class to handle subwallets
** Note: We should decide how we want to handle this in the future. This
way subwallets can only be managed using the multitenant controller
because otherwise updating the tenant JWT is not possible in the
AriesAgentController.

Author: morrieinmaas