Add a helm chart for deploying Python services to Kubernetes

[gilesknap]

The fastcs helm chart should be made generic and included in this repo
https://github.com/DiamondLightSource/FastCS/blob/b46ee3e1607896ba91bfb7180d5c74d31129671d/Charts

Notes:-

• For a project that publishes containers referred to by the helm chart, the _containers.yml workflow should be added to the needs of _helm in ci.yml.
• inspect the values of editable and autostart in the values.yaml file of the specified IOC (TODO: at present it uses the p47-services source code to do so but this should be determined from the cluster in future).
• also see https://github.com/epics-containers/p47-services/blob/f6e6aa6383db204f4e9a3b7b05f9234562f10247/debug.py for how the editable and autostart features are used.
• inspection of the values of editable and autostart in the values.yaml file of the specified IOC currentl uses the p47-services source code to do so but this should be determined from the cluster in future.
• note that symlinks from the /schemas folder to the individual Charts/xxx/values.schema.json should be supplied (document the manual process or automate it) AND we need a solution like this:https://github.com/DiamondLightSource/FastCS/blob/b46ee3e1607896ba91bfb7180d5c74d31129671d/schemas/fastcs-service.schema.json for making a schema for the services repository - but where should that go?

[coretl]

Related to #226