Allow resources to contain unexported fields

[scothis]

Using unexported fields in Kubernetes resources is not common, but does happen. Previously, these fields would cause cmp.Diff to panic. Now, we ignore the content of unexported fields when computing a diff. As the diff is for logging and test assertions this is relatively safe.

Semantic equality is used for detecting when a managed resource needs to be updated. Custom equality func can be defined separately as needed.

Refs #484

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 80.00000% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 61.12%. Comparing base (3180680) to head (09436ab).

Files	Patch %	Lines
testing/subreconciler.go	0.00%	2 Missing :warning:
testing/webhook.go	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #487 +/- ## ========================================== + Coverage 61.03% 61.12% +0.09% ========================================== Files 27 28 +1 Lines 2556 2562 +6 ========================================== + Hits 1560 1566 +6 Misses 909 909 Partials 87 87 ```

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[mamachanko]

[question, non-blocking]: @scothis when you say

Custom equality func can be defined separately as needed.

are you meaning that there could potentially be a follow-up PR? I am asking because afaik there's currently no way to provide a custom equality func, or is there?

[scothis]

@mamachanko I was basing it on this comment https://github.com/vmware-labs/reconciler-runtime/issues/484#issuecomment-1958682986

[neowulf]

@scothis this fix works! Thank you again for the quick turnaround!

[scothis]

@neowulf cool, I'll circle back to Max's feedback tomorrow.

[mamachanko]

Thank you @scothis !

[vmwclabot]

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