Remove loader support for nodeup tasks not used in models

[johngmyers]

/kind cleanup

[justinsb]

I'm surprised this one isn't used; I'm going to dig into why it isn't / where it came from.

On removing the serialization, I do think it's a good idea to clean up the custom deserialization. I do have a longer term idea that we should put less logic into nodeup, and pass it more of these tasks (as I think the logic in nodeup is much more opaque, harder to understand, harder to change). But I don't think that is incompatible with removing the "legacy" deserialization. (And we should just rely on yaml/json deserialization if we start passing raw tasks, IMO)

[justinsb]

Yup, you're right ... unused legacy code. Thanks @johngmyers!

/approve
/lgtm

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[johngmyers]

I find tasks in Go code to be easier to understand and change than those in YAML. My IDE can cross-reference the Go code.

[johngmyers]

/retest

[johngmyers]

/retest