Fix CI using epics containers

[jennmald]

• Uses GitHub container repository and epics containers as a replacement for the docker containers
• GH actions now starts docker, creates the directories for area detector, starts the docker containers using a compose.yaml file, and runs all pyepics tests
• No longer need to skip the motor sim tests using these containers

Things to do (will discuss more when Max returns)

• move epics-services-for-ophyd somewhere more central
• update the NDOverlays addition, issue here: 'NOverlays' is undefined epics-containers/ibek-support#70

Open to feedback :)