Handle KongIngress deprecation in admission webhook and in KongIngress validation rules

[rainest]

What this PR does / why we need it:

Alternative to #5015. Deprecates KongIngress in the sense that it's still available for the time being, but results in logs instructing users to migrate rather than removing it immediately.

Which issue this PR fixes:

For #4720 but not using auto-resolve since this isn't targeted to main.

Would need a follow-up "Remove KongIngress support" issue.

Notes:

I did leave in the checks for route and service even though CEL now blocks them. I figure it doesn't really hurt anything to have them there under normal circumstances, and we often had abnormal circumstances because users forget to update CRDs.

Added a Service webhook handler also. I don't really love having that in place for such a common resource, but it is at least only temporary: we'd remove it once we actually remove KongIngress.

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

[codecov]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (dce791d) 75.5% compared to head (8c6c952) 75.5%.
Report is 1 commits behind head on main.

❗ Current head 8c6c952 differs from pull request most recent head 057d0da. Consider uploading reports for the commit 057d0da to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #5022     +/-   ##
=======================================
- Coverage   75.5%   75.5%   -0.1%     
=======================================
  Files        167     167             
  Lines      18848   18836     -12     
=======================================
- Hits       14238   14226     -12     
- Misses      3783    3785      +2     
+ Partials     827     825      -2     

Files	Coverage Δ
internal/dataplane/kongstate/kongstate.go	86.2% <100.0%> (+1.5%)	⬆️
internal/admission/handler.go	61.0% <78.2%> (+1.5%)	⬆️

... and 6 files with indirect coverage changes

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[czeslavo]

I've rebased the PR onto main and added CEL validations.

[czeslavo]

I had to rebase (conflict in go.sum), sorry @pmalek 😞