Ingress operator should use granular roles on GCP

Description of problem

The Ingress Operator should use granular roles in its CredentialsRequest per CCO-249. A change to use granular roles merged after the release-4.15 branch cut. This change needs to be backported for 4.15.0.

Version-Release number of selected component (if applicable)

4.15.0

How reproducible

Easily.

Steps to Reproduce

1. Launch an OCP 4.15 cluster on GCP.
2. Check the ingress operator's CredentialsRequest: oc get -n openshift-cloud-credential-operator credentialsrequests/openshift-ingress-gcp -o yaml

Actual results

The CredentialsRequest uses a predefined role:

spec:
  providerSpec:
    apiVersion: cloudcredential.openshift.io/v1
    kind: GCPProviderSpec
    predefinedRoles:
    - roles/dns.admin

Expected results

The CredentialsRequest should specify the individual permissions that the operator requires:

spec:
  providerSpec:
    apiVersion: cloudcredential.openshift.io/v1
    kind: GCPProviderSpec
    permissions:
    - dns.changes.create
    - dns.resourceRecordSets.create
    - dns.resourceRecordSets.update
    - dns.resourceRecordSets.delete
    - dns.resourceRecordSets.list

Additional info

https://github.com/openshift/cluster-ingress-operator/pull/844 merged in the master branch for 4.16 and needs to be backported to the release-4.15 branch.