Build and push a scorecard image with CI

[ebaron]

Our CI should detect when a new scorecard image needs to be built, perform the build and push it to Quay. One way we could do this is the following:

1. Use yq to parse the bundle's scorecard config within bundle/tests/scorecard/config.yaml and extract the scorecard image repository:tag, and store it in a variable.
2. Use podman to query whether the image tag exists already.
3. If it doesn't, build the scorecard image with make scorecard-build CUSTOM_SCORECARD_IMG=<variable from step 1>
4. Push to Quay using the push-to-registry action.