Follow-up from "GraphQL: Allow to request pipelines by id"

However, I don't think we even need the batchLoader here in the first place. If you take a look at what's it's used for: https://docs.gitlab.com/ee/development/graphql_guide/batchloader.html it doesn't seem like this fits what we need as we specifically have a PipelinesFinder to bunch and perform optimized queries.

That also means, I don't believe what we have right now for iid / sha are correct. The current code makes it seem like we can query for multiple iid/sha when this is false. We can only query single iid/sha right now. And even multiple pipelines with the same sha will only return one of them. We should fix this in a follow-up.