Get Devices incorrectly returns devices that have failed to connect

[RJCD-Diamond]

v1.0.0 has just been installed on b21. Upon spinning up BlueAPI the saxs and waxs detectors have failed to connect because the IOCS are not on. This is reflected in the startup logs and is expected.

However Get Devices still returns the saxs and waxs detectors.

Steps To Reproduce

Steps to reproduce the behavior:

1. Go to https://b21-blueapi.diamond.ac.uk/docs#/Device/get_devices_devices_get
2. Click on "Try it Out" Then "Execute"
3. Scroll down through the return json and waxs and saxs are shown towards the bottom
4. See that this is in error

Acceptance Criteria

• Have blueapi startup, fail to connect to the missing devices, then show the same devices that connect in the logs as are returned in Get Devices

[RJCD-Diamond]

b21-beamline-b21-blueapi-0-blueapi.log

See startup logs

[RJCD-Diamond]

B21 BlueAPI is not being used for anything currently, so there is no risk in deleting the pod/restarting etc.

[callumforrester]

This is happening because Blueapi captures exceptions raised during device instantiation but not during connection. It throws those away (the exceptions variable is unused).

It can probably be refactored to be used in the same way is instantiation exceptions, however this code could be simpler so whoever does this is best off just doing the dodal refactoring outlined in #759 and DiamondLightSource/dodal#964, and giving themselves a nice API to work with in blueapi.

[callumforrester]

Failing test: #1145