RFC: workflow hints section

[jdidion]

We are beginning to have features in the development spec that leverage workflow-level hints to the runtime engine, e.g. the allowNestedInputs flag described in #359. Such hints do not really belong in meta. I propose that we add a hints section to workflow that has identical semantics to task hints.

[patmagee]

As I Mentioned in the linked PR, I think this is ultimately a good Idea. we already have 1 use case for hints being in the workflow as opposed to just the task which likely means there are going to be other uses that we come across

[rhpvorderman]

This would indeed be best. It was only added in meta because of a lack of a hints section.