Add crossplane framework for testing

[sjberman]

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Problem: We want a way to verify nginx configuration reliably in our tests. This is especially useful when introducing new policies, without the desire for testing nginx functionality directly.

Solution: Added a framework for getting the nginx config and passing through crossplane into a structured JSON format for easier parsing.

Because we now use a local container for crossplane in our functional tests, we'll only support running these tests in a kind cluster.

Closes #2014

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• [x] I have read the CONTRIBUTING doc
• [x] I have added tests that prove my fix is effective or that my feature works
• [ ] I have checked that all unit tests pass after adding my changes
• [ ] I have updated necessary documentation
• [x] I have rebased my branch onto main
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Release notes

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