⚠ REMOVE extension api from main branch

[acmenezes]

Description

The intent is to remove this API and its controllers for the v1.0.0 release. Once we've released 1.0.0, we plan to re-introduce the Extension API and controllers.

@joelanford, please take a look and tell me if that's what you had in mind. I did a flat removal of all the references to the api as well. Didn't try to circumvent or redesign around any errors. Any suggestions or changes are welcomed. Saving this as a draft PR to be safe.

My question, and I think it's an important one, would we pull the main branch's code to some secondary branch as a reference for after v1.0.0 before merging this if we plan to reintroduce it?

Solves #735

Reviewer Checklist

• [ ] API Go Documentation
• [ ] Tests: Unit Tests (and E2E Tests, if appropriate)
• [ ] Comprehensive Commit Messages
• [ ] Links to related GitHub Issue(s)

[netlify[bot]]

✅ Deploy Preview for olmv1 ready!

Name	Link
🔨 Latest commit	5f838135a940bcc0d650582dc22e264976e920b1
🔍 Latest deploy log	https://app.netlify.com/sites/olmv1/deploys/66437b470d70e70008b3e7a8
😎 Deploy Preview	https://deploy-preview-820--olmv1.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 66.66667% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 81.80%. Comparing base (6d73b73) to head (ca00f4a).

Files	Patch %	Lines
...nternal/controllers/clusterextension_controller.go	57.14%	4 Missing and 2 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #820 +/- ## =========================================== + Coverage 71.02% 81.80% +10.78% =========================================== Files 17 15 -2 Lines 1301 907 -394 =========================================== - Hits 924 742 -182 + Misses 304 120 -184 + Partials 73 45 -28 ``` | [Flag](https://app.codecov.io/gh/operator-framework/operator-controller/pull/820/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=operator-framework) | Coverage Δ | | |---|---|---| | [e2e](https://app.codecov.io/gh/operator-framework/operator-controller/pull/820/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=operator-framework) | `59.75% <61.11%> (+17.02%)` | :arrow_up: | | [unit](https://app.codecov.io/gh/operator-framework/operator-controller/pull/820/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=operator-framework) | `73.76% <66.66%> (+10.16%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=operator-framework#carryforward-flags-in-the-pull-request-comment) to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[joelanford]

I don't think we need to save the code off. The git history is there, so we can just come back to the commit prior to this PR if necessary.

But I suspect we don't even do that. I think it is more likely that we'll essentially copy ClusterExtension back over to Extension and make the few tweaks necessary for it to work as a namespace-scoped API. And we'll do a similar thing for the controller.

[acmenezes]

IMO the lint failures can be addressed via a //nolint:unused comment for now and be updated in #747 when they are used again.

This should help keep the scope of this PR smaller

@everettraven good idea. I just added the comments there. I think no more lint issues are found. Thanks.