🌱 Add unit tests for MachinePools for webhooks and cc controller

[willie-yao]

What this PR does / why we need it:
This PR adds unit tests for MachinePool workers in ClusterClass for the following files:

• internal/webhooks/cluster_test.go
• internal/webhooks/clusterclass_test.go
• internal/webhooks/patch_validation_test.go
• internal/controllers/clusterclass/clusterclass_controller_test.go

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes part of #10028

/area clusterclass

[sbueringer]

Thank you very much for working on this!

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 2cfbc0418abdaed17295d6e06af11a63bc981e05

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sbueringer

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