Consider moving CRDs to separate Go module

[kate-goldenring]

If in a separate go module, other projects, such as the spin-kube plugin could reference it.

Context: spinkube/spin-plugin-kube#88

[endocrimes]

It should be able to reference it already? - transitive dependency conflicts shouldn't be much of an issue between the plugin and the operator (iirc it doesn't mostly to template nicer yaml than just encoding a struct would give you)

[kate-goldenring]

@endocrimes good point. we can import the entire spin-operator module and use the api types.