Simplify cluster scope creation in controllers unit tests

[willie-yao]

/kind cleanup

What needs cleanup:
The unit tests in the controllers package repeatedly call NewClusterScope which runs a lot of unnecessary code and requires extra setup.

Describe the solution you'd like
Have separate tests for NewClusterScope. Replace calls to NewClusterScope in unit tests with definitions to a literal &ClusterScope{...}.

Files to change:

• All unit tests files in the controllers package

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

[willie-yao]

Original discussion: #4208 (comment)

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/lifecycle stale

[nawazkh]

/remove-lifecycle stale