feat(custom_entity): add KCE controller

[randmonkey]

What this PR does / why we need it:

The initial (and largest) part of KongCustomEntity controller.

Which issue this PR fixes:

Major part of #5976

Special notes for your reviewer:

It invokes a procedure to get referred entities of plugins to fill IDs of the entities to the "foreign" fields of custom entities. It is finished in getServiceIDFromPluginRels method. I think we can change the getPluginRels method to store pointers to the entities instead of identifiers, because with the entities itself we can do more operations on it.

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: Patch coverage is 43.00792% with 216 lines in your changes missing coverage. Please review.

Project coverage is 74.3%. Comparing base (763d7d1) to head (8a704cd).
Report is 40 commits behind head on main.

Files	Patch %	Lines
...trollers/configuration/zz_generated_controllers.go	0.0%	92 Missing ⚠️
internal/dataplane/kongstate/kongstate.go	56.8%	63 Missing and 10 partials ⚠️
internal/dataplane/sendconfig/inmemory.go	0.0%	9 Missing and 1 partial ⚠️
internal/store/store.go	52.3%	10 Missing ⚠️
internal/dataplane/translator/translator.go	18.1%	8 Missing and 1 partial ⚠️
internal/dataplane/deckgen/deckgen.go	16.6%	4 Missing and 1 partial ⚠️
internal/manager/schema_service.go	37.5%	5 Missing ⚠️
internal/store/fake_store.go	42.8%	3 Missing and 1 partial ⚠️
internal/controllers/utils/utils.go	0.0%	2 Missing and 1 partial ⚠️
internal/dataplane/kong_client.go	40.0%	2 Missing and 1 partial ⚠️
... and 1 more

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #6055     +/-   ##
=======================================
- Coverage   74.6%   74.3%   -0.3%     
=======================================
  Files        194     198      +4     
  Lines      18861   19743    +882     
=======================================
+ Hits       14072   14677    +605     
- Misses      3814    4061    +247     
- Partials     975    1005     +30     

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[pmalek]

Minor typos and we're close to merging this.

Just for clarification about fakes vs mocks vs stubs which I believe is already incorrectly used across the codebase:

We're referring to fakes in our codebase to entities that are service a purpose that is reserved for stubs.

Fakes are meant to be implementations that perform some sort of a shortcut (e.g. use memory backed storage instead of DB). Stubs are meant to

provide canned answers to calls made during the test, usually not responding at all to anything outside of what’s programmed.

[pmalek]

One last thing which I believe is important: can we add at least 1 example manifest to https://github.com/Kong/kubernetes-ingress-controller/tree/9dfe2123b277e8ba418152ff1536c9e696786a7f/examples that will use the custom entity CRD?

[randmonkey]

One last thing which I believe is important: can we add at least 1 example manifest to https://github.com/Kong/kubernetes-ingress-controller/tree/9dfe2123b277e8ba418152ff1536c9e696786a7f/examples that will use the custom entity CRD?

I would include this in PR for integration tests.