chore(docs): deprecate KongIngress' proxy and route in favor of annotations

[czeslavo]

What this PR does / why we need it:

Adds deprecation comments to all KongIngress fields that have their replacement in form of an annotation.

Which issue this PR fixes:

Part of #2941.

Special notes for your reviewer:

PR Readiness Checklist:

Complete these before marking the PR as ready to review:

• the CHANGELOG.md release notes have been updated to reflect any significant (and particularly user-facing) changes introduced by this PR

[pmalek]

Do you mind linking here the relevant docs change as well?

[czeslavo]

Do you mind linking here the relevant docs change as well?

Do you mean a preview from docs.konghq.com? Once we merge it, I will update the PR on the docs repo side that's using the generated docs (Kong/docs.konghq.com#4813). For now you may look at the rich view of the md file: https:/Kong/kubernetes-ingress-controller/blob/8a9a7b854678f2671435f34d2ea3f6e7f68ce692/docs/api-reference.md

[pmalek]

Do you mind linking here the relevant docs change as well?

Do you mean a preview from docs.konghq.com? Once we merge it, I will update the PR on the docs repo side that's using the generated docs (Kong/docs.konghq.com#4813). For now you may look at the rich view of the md file: https:/Kong/kubernetes-ingress-controller/blob/8a9a7b854678f2671435f34d2ea3f6e7f68ce692/docs/api-reference.md

Ok that's fine 👍 Let's merge this one then.