fix: Revert CRD apiVersion

[tumido]

I was a bit reckless when upgrading CRD from v1beta1 to v1 in #607. I did two mistakes:

1. Simple versions (version) are no longer available, only the long form versions is supported
2. A schema field is a required in v1. That means, even enforcing v1 api with an empty spec like this:

   schema:
     openAPIV3Schema:
       type: object
   

   would require users to create every object with --validate=false flag for now, and I don't think that's what we want.

Let's revert back to v1beta1.

Also.. fixing a typo s/cdrs/crds/g and making event-source CRD name consistent with pkg/apis/eventsources/

I've tried implementing the OpenAPIV3Schema in another PR #624, but I'm not much successful with that so far... Let's discuss that option there.

[nfp007]

Unable to apply issue is fixed by this PR