Create a system test environment

Testing with mocks gives us a good way to make sure UI elements work but there is currently no easy way to test that infrastructure works. We have hit this a couple of times recently:

* A bug @EmsArnold found where caweblib is not connecting and causing the UI to not render
* Trying to test https://github.com/DiamondLightSource/atlas/issues/58
* Trying to test the mock assumptions made in https://github.com/DiamondLightSource/atlas/pull/44

As it stands the quickest way to test this is deploy it onto a beamline and run it. This is probably ok for now while the waffle project is moving fast but ultimately we will need to test things offline. To do this we will need to:

* Run up an oauth proxy
* Run a BlueAPI - configured to point to some plans
* Run some dummy IOCs that we can read some values from
* Point to a test graphQL where we can read/change things without affecting prod
* Run some automated tests against this

BlueAPI has some system tests that do some of this but we need to integrate it all into a system that is well documented and easy for a support group to configure for their apps.