(Helm) add checksum to config to force restart on changing config

[DiamondJoseph]

When Helm mounts config as a configmap, changes to that configmap are not reflected in the pod until the files are read again. For something like root app settings, that means changes will not be picked up until the container is restarted. One way to accomplish that is adding a checksum annotation to the container based on the contents of the configmap.

See e.g. https://github.com/DiamondLightSource/blueapi/blob/d8a989cc6e2740e9eb3e8adf356a2c1b5ce41d3b/helm/blueapi/templates/statefulset.yaml#L18