Red Hat registry service account needed to download UBIs

Red Hat is migrating its container registry from `registry.access.redhat.com`, which is unauthenticated, to `registry.redhat.io`, which requires authentication. The recommended authentication method is to to use registry tokens, but it looks like Podman authenticates with username/password.

Either way, each team that installs the Toolkit will need to [create a registry service account](https://access.redhat.com/terms-based-registry/) and store those credentials in their Toolkit installation. The Toolkit will need these credentials so that it can download UBIs.

For example, see the Get This Image tabs in [ubi8/openjdk-11](https://catalog.redhat.com/software/containers/ubi8/openjdk-11/5dd6a4b45a13461646f677f4) or [ubi8/nodejs-14](https://catalog.redhat.com/software/containers/ubi8/nodejs-14/5ed7887dd70cc50e69c2fabb):
- Unauthenticated: "To support our existing users and users to come, we will be transitioning our product portfolio and customers to a new container registry. The new registry uses standard OAuth mechanisms to provide customers with the ability to configure their systems to pull containerized content using static tokens or their Red Hat login. Customers are encouraged to begin using the new registry as their preferred authentication method."
- Using Red Hat login: "For best practices, it is recommended to use registry tokens when pulling content for OpenShift deployments."
- Using registry tokens: "You will need to create a registry service account to use prior to completing any of the following tasks."