[Docs] Restrict security context of pods by default

The operator pod and the broker pods can run with a safer and restricted security context without issues. Restricting the security context of the pods by default allows to deploy a cluster of brokers also in Kubernetes namespaces with the restricted policy.

The minimal changes to run the pods in Kubernetes namespaces with the restricted policy:

• spec.containers[*].securityContext.allowPrivilegeEscalation: false
• spec.initContainers[*].securityContext.allowPrivilegeEscalation: false
• spec.ephemeralContainers[*].securityContext.allowPrivilegeEscalation: false

• spec.securityContext.runAsNonRoot: true
• spec.containers[*].securityContext.runAsNonRoot: true
• spec.initContainers[*].securityContext.runAsNonRoot: true
• spec.ephemeralContainers[*].securityContext.runAsNonRoot: true

• spec.securityContext.seccompProfile.type: RuntimeDefault
• spec.containers[*].securityContext.seccompProfile.type: RuntimeDefault
• spec.initContainers[*].securityContext.seccompProfile.type: RuntimeDefault
• spec.ephemeralContainers[*].securityContext.seccompProfile.type: RuntimeDefault

• spec.containers[*].securityContext.capabilities.drop: ["ALL"]
• spec.initContainers[*].securityContext.capabilities.drop: ["ALL"]
• spec.ephemeralContainers[*].securityContext.capabilities.drop: ["ALL"]