controller-gen doesn't support deeply nested maps

[matthchr]

This comes up for example here:
microsoft.machinelearning/v20170101/ExampleRequest the Inputs field which has the type map[string][][]map[string]v1.JSON (after the pipeline stage that replaces AnyTypes).

[matthchr]

There's a PR out to support this here, which I think is based on @Porges PR here

[Porges]

My PR probably won’t fix this particular case: maps containing arrays are currently only allowed to have arrays of strings, which is a different restriction to the one that I am lifting. (See: kubernetes-sigs/controller-tools#518 (comment).) However, this will be an easy restriction to lift.

[Porges]

Done!