InstanceGroup Requires "OpenShift or Kubernetes credential"

[neevnuv]

InstanceGroup CRD sets credential_name as required even tho it is not required when specifying the InstanceGroup. I propose we remove the credential_name from required.

Instance Group CRD required

Moreover, there should be a fieldDependency set in the ClusterServiceVersion, for the InstanceGroup: For example, the credential_name only exists for containerGroups:

     - displayName: Container Group
        path: is_container_group
        x-descriptors:
        - urn:alm:descriptor:com.tectonic.ui:booleanSwitch
      - displayName: OpenShift or Kubernetes credential
        path: credential_name
        x-descriptors:
        - urn:alm:descriptor:com.tectonic.ui:text
        - urn:alm:descriptor:com.tectonic.ui:fieldDependency:is_container_group:true

While "policy_instance_minimum" and "policy_instance_percentage" only exists for instanceGroups (and not containerGroups):

    - displayName: Policy Instance Percentage
       path: policy_instance_percentage
       x-descriptors:
       - urn:alm:descriptor:com.tectonic.ui:int
       - urn:alm:descriptor:com.tectonic.ui:fieldDependency:is_container_group:false
     - displayName: Policy Instance Minimum
       path: policy_instance_minimum
       x-descriptors:
       - urn:alm:descriptor:com.tectonic.ui:int
       - urn:alm:descriptor:com.tectonic.ui:fieldDependency:is_container_group:false