feat(operator): add release workflow

[jsenko]

• This workflow automates all tasks for the operator release, including creating PRs to the OperatorHub and Operator Marketplace repos, however manual intervention might be needed for those PRs to be merged.
• Since I could not fully test the workflow in an actual release, some supervision will be needed when first running this for real.
• After the first release is done, some changes have to be made since the subsequent releases have to reference the previous bundle in the channel. There is a couple of TODOs for this task.
• I've also modified the PR check workflow to improve the run time by skipping local test mode, which will only run on push.
• I've refactored Minikube setup steps into a composite action. We might use this approach in the future for e.g. Slack notifications.
• I found out that the operator check workflow was not running he OLM tests by mistake, and I had to fix a few things we missed as a result.
• I've also changed the image repository names for operator-related images (operator, bundle, and catalog) to apicurio-registry-3-operator-* to differentiate them from the legacy images.

[EricWittmann]

LGTM merge at your discretion

[jsenko]

LGTM merge at your discretion

Thank you