Update OpenShift Release Process

[pseudomuto]

Install preflight binary on Linux machines

Adding preflight to the list of OpenShift binaries installed. For now,
this is only available on Linux machines and won't be added to anyone
using Darwin.

Publish operator and bundle images for RedHat/OpenShift

Updating the build/release scripts to handle publishing the bundle
images and running preflight on them.

The publish-openshift script downloads the tagged release from
DockerHub, retags it correctly for the RedHat scanning repo, pushes it,
and finally runs the preflight check on it.

The openshift-bundle script largely does the same, only it publishes the
bundle image rather than the operator image. The same script is used for
both the certified and marketplace bundles. Passing `MARKETPLACE=1` will
use the marketplace bundle values rather than the certified ones
(default).

Checklist

• [ ] I have added these changes to the changelog (or it's not applicable).