Support service-level security context configuration
What does this MR do?
Allows admins to configure security context settings at the service level.
Why was this MR needed?
Security needs vary widely from service to service and it makes sense to allow admins to only provide heightened privileges to those services that actually require them.
What's the best way to test this MR?
Configure a kubernetes runner with two services, one with security context fields and the other without. Verify via the k8s api that the container specs for the spawned runner pod have the respective contexts configured. Add service_container_security_context configuration to the runner to verify that it is still inherited by service containers but is overwrite-able.