✨ Extend scale test & improve controller-runtime dashboard

[sbueringer]

Signed-off-by: Stefan Büringer buringerst@vmware.com

What this PR does / why we need it:
Adds various features to the scale test & makes a small improvement to the controller-runtime dashboard

Improvements to the scale test:

• Deploy additional ClusterClasses
• Consistent overwrites for input fields via variables
• Supports testing the cross-ns ClusterClass feature
• Supports testing Runtime Extensions

Kudos to @fabriziopandini & @chrischdi for prototyping most of these changes and the collaboration on scale testing

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 #

[k8s-ci-robot]

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[sbueringer]

Ready for review, but will only become green after #11352 is merged.
/hold

/assign @chrischdi @fabriziopandini @lentzi90