feat: New ScalingSet CRD to deploy isolated interceptors+scalers

[JorTurFer]

Provide a description of what has been changed

Checklist

• [ ] Commits are signed with Developer Certificate of Origin (DCO)
• [ ] Changelog has been updated and is aligned with our changelog requirements
• [ ] Any necessary documentation is added, such as:
  • README.md
  • The docs/ directory
  • The docs repo

Fixes https://github.com/kedacore/http-add-on/issues/241

[JorTurFer]

I appreciate your feedback, I'll review it, but don't worry about reviewing the PR for the moment as it's still a WIP and there are a couple of pending stuff, like propagating the status info the the CRD, documentation, more test coverage , etc

You can review it if you want, but there can be multiple changes until the final version :)

[JorTurFer]

I'm removing the changes applied to my local branch

[JorTurFer]

I've been talking about this with @zroubalik and to not lock you with the code refactor, we will agreed with merging this PR as it is (it works actually) and I'll open a followup PR in a few days/weeks (before the release for sure) adding the pending stuff to complete this PR (such as but not exclusive):

• Documentation
• CRD Status propagation
• Autoscaling
• Support for global configurations (timeouts, TLS, watched namespaces, etc...)

[kahirokunn]

This feature is great! I can't wait to start using it!