narrow down typing for hook and step functions

[davidjgoss]

🤔 What's the problem you're trying to solve?

The TypeScript typings for the functions users pass in to hooks and steps should have the return value appropriately typed so it's clear what you can and can't influence from the function.

Currently the return value for all of them is typed as

any | Promise<any>

We should make these more specific.

We should also check the signature of the callback function for that style of step, for the same reason.

✨ What's your proposed solution?

Here's what I think each function should be able to return (in each case it could be a plain value of this type, or a promise that resolves to one).

• BeforeAll, AfterAll - void
• Before, BeforeStep - void | 'skipped'
• (actual steps) - void | 'skipped' | 'pending'
• AfterStep, After - void

This might be a breaking change, although we call allow a fallback of any at the end of the type union so it's permissive but still surfaces hints as users type - that would probably be the ideal.

📚 Any additional context?

Originally discussed in #2038 (comment)

[davidjgoss]

I took a quick run at this today and found it difficult given how spread out our code and types for user code is, with SupportCodeLibraryBuilder etc. It might be one to return to once we've had a chance to simplify that area a bit.