Add broker transformation test to upgrade tests

[mgencur]

Proposed Changes

• Refactor broker transformation test so that it can be used in upgrade tests (this will also be reused in knative-extensions/eventing-kafka-broker, see WIP pull request )
• Include Broker transformation test in upgrade test suite
• Fix DurableFeature. The FeatureF must be a function that can be called multiple times on demand, and it will create a new feature every time - with different resources to prevent clash with existing resources.

Pre-review Checklist

• At least 80% unit test coverage
• E2E tests for any new behavior
• Docs PR for any user-facing impact
• Spec PR for any new API feature
• Conformance test for any change to the spec

Release Note

Docs

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.45%. Comparing base (c91a9d8) to head (5928540).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8190   +/-   ##
=======================================
  Coverage   67.45%   67.45%           
=======================================
  Files         371      371           
  Lines       18039    18039           
=======================================
  Hits        12169    12169           
  Misses       5091     5091           
  Partials      779      779           

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[mgencur]

/test unit-tests

[matzew]

/lgtm
/approve

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: matzew, mgencur

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