[WIP] Use and test KafkaSource v1 API

[pierDipi]

Replace usages of v1beta1 KafkaSource to v1 KafkaSource

Part of #3953

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: pierDipi

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[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 45.12%. Comparing base (024dd1f) to head (0340e6d).
Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
...rnalskafkaeventing/v1alpha1/consumer_validation.go	0.00%	2 Missing ⚠️
control-plane/pkg/autoscaler/keda/keda.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4138   +/-   ##
=======================================
  Coverage   45.12%   45.12%           
=======================================
  Files         270      270           
  Lines       15995    15995           
=======================================
  Hits         7218     7218           
  Misses       8050     8050           
  Partials      727      727           

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[pierDipi]

/retest-required

[pierDipi]

This can be merged only after 1.16 is out

[pierDipi]

/retest

[knative-prow]

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

Test name	Commit	Details	Required	Rerun command
upgrade-tests_eventing-kafka-broker_main	0340e6d	link	true	/test upgrade-tests
reconciler-tests-namespaced-broker_eventing-kafka-broker_main	0340e6d	link	true	/test reconciler-tests-namespaced-broker

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