Revisit making an RE for ophyd-async devices

[DominicOram]

From bluesky/ophyd-async#81 it sounds like maybe we don't have to make an RE before initialising every device. Even if we do have to we should push this more into the device creation logic in dodal so we don't end up having to litter code with RunEngine() # A RE is needed to start the bluesky loop.

Acceptance Criteria

• There is no longer a need to make an RE before every ophyd-async device
• We remove places where we're doing this