Add complex overlay composition test

[ioandr]

This PR adds a test with a complex kustomization scenario that combines patches with custom resources and generators.

The provided test does not reach the assertion phase, since it causes kustomize to fail with:

recursed merging from path: ... may not add resource with an already registered id

Related with:

• Support composition in kustomize #1251
• Support a high-level merge behavior in kustomize #1292

nit: Some fields of the expected output YAML strings in comments might need reordering.

[k8s-ci-robot]

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[monopole]

👍 👍

/lgtm

Great starting point.