Add test to ensure Operator SDK bundle isn't changed by accident

[killianmuldoon]

Currently the Operator SDK bundle generated for this repo uses underlying kustomize files which are also used for dev work. It would be good to have a CI check to ensure nothing in these files changes by accident. This could just be a make bundle followed by a git diff on the output, comparing master with the PR.

I'm not sure how the release process for those bundles works, so I'm not sure if we would need to explicitly exclude versions or if there's other complications.