Change default installation namespace on OpenShift

[sasagarw]

What this PR does / why we need it:

• updates the default namespace for openshift to openshift-operators-redhat.
• updates the reference from loki.openshift.io -> loki.grafana.com

Which issue(s) this PR fixes:
Fixes #5440

Special notes for your reviewer:

Checklist

• Documentation added
• Tests updated
• Add an entry in the CHANGELOG.md about the changes.

[xperimental]

Looks okay, only some minor changes.

While looking at the PR I came across the --install-mode which is currently set to OwnNamespace. Is this still correct when we plan to have the operator running in openshift-operators-redhat but Loki deployed to openshift-logging?

[sasagarw]

@xperimental yeah it works fine when I try to deploy operator in openshift-operators-redhat and lokistack in openshift-logging. Didn't find any issue in running the complete stack.

[xperimental]

Almost there, something just occurred to me while looking at it the second time: The later instructions in hack_loki_operator.md still correctly reference the openshift-logging namespace because we intend to run Loki in that namespace, but the first command referencing the namespace will fail if it does not exist.

Does it make sense to add a paragraph to the doc for creating the namespace before trying to add resources to it? In the document that would be before adding the AWS secret.