Add generator function to accepted hook types

[villasv]

Summary

Another go at #10066, generators weren't included in the last PR (#10480).
This is a redo of PR #10526 cause I lost that fork :-P

Test plan

Added more type tests.

Details

Reviewers will notice some ugly stuff going on. For starters, that isGeneratorFn type guard is checking against the GeneratorFunction interface, which doesn't seem to be the correct approach here (it's badly misunderstood just like Function). If we try to use GeneratorFunction as the receiving type for hook functions, it will fail.

So I declared a makeshift interface that should hold any generator function. But then, for some reason the type inference of a few fn.call inside jest-circus broke. I have no idea why, but manually providing the type arguments was possible to please the compiler.

Then another type inference gone awry and I had to specify the any type for the returnedValue variable, otherwise TypeScript inferred its value as possibly a Generator (thanks for nothing on the above type guard).

So all in all I'm not very pleased with the way things are, but I wasn't able to remove any of this cruft. If someone else feels like trying to, they're welcomed to try and supersede this PR.

[villasv]

Hey @SimenB, just a ping. I think the CI should have passed on this.

[SimenB]

thanks!

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