WIP chore(source): code cleanup, decouple and isolate logic

[ivankatliarchuk]

Description

I was trying to implement support for istio networking.istio.io/v1. The approach is:

• support networking.istio.io/v1alpha3
• add support for networking.istio.io/v1

Size of PR is quite big, as added bunch of tests, and new files do require licences headers. I could split this PR on mulitple.

Tried to add support for v1alpha3 and v1 Istio apis. The code is here gofogo#10. However the code coupling is too high, there is a benefit to create specific packages in sources to reduce coupling. In isolation is easier to improve code coverage as well. This will also enable us to improve code coverage through isolated testing.

Not resolves, but will simplify implementation for following issues
Relates #4473
Relates #2798
Relates #4786

The idea is to support multiple api versions for istion "networking.istio.io/v1alpha3" and "networking.istio.io/v1" for a period of time. this require some refactoring beforehead, as in source directory code is tightly coupled

• no chnges to business logic or current functionality
• added more descriptive logs to even handler
• added tests for even handlers

Checklist

• Unit tests updated
• End user documentation updated

[k8s-ci-robot]

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[k8s-ci-robot]

@ivankatliarchuk: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-external-dns-licensecheck	222be63	link	true	/test pull-external-dns-licensecheck

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[ivankatliarchuk]

/kind cleanup
/label tide/merge-method-squash

[ivankatliarchuk]

Most of the work done in another PR