adding hooks to expectations, with prep to make GE and hooks interface neatly
per pipeline should be supported as well as per solid is, but tbh the use case for expectation results as I see it is way more likely to be limited to a few solids.
Right now it does get called for every expectation result, but it should be easy to provide native hook supports for 'only respond to ERs with a given label'
This is a case where I think our "list" approach fails us and we may want to consider a different type of hook and processes one event at a time. For hooks of this nature I'm concerned about long-running computations where getting the events only at the end will feel like a bug. We've spent a bunch of effort making the whole core streaming so want to keep that going.
I think we should have a generic event_hook with expectation_hook built on top of it. Further filtering can just be implement as custom event_hook