Refactoring fetchQueryOverInterface within QueryManager

[Poincare]

Working on #471.

TODO:

• Update CHANGELOG.md with your change
• Make sure all of the significant new logic is covered by tests
• Rebase your changes on master so that they can be merged easily
• Make sure all tests and linter rules pass

[stubailo]

Is there some way we can make this return less stuff? For example, document, definition, and selection set seem a bit redundant.

[Poincare]

Yeah, I'm still working on the refactor. The final stuff that it will return will probably only be the document and nothing else.

[stubailo]

OK, I spoke too soon

[Poincare]

@stubailo what do you think

[stubailo]

@Poincare do you think it would be valuable to start splitting this into multiple files? or would that just make the code harder to follow?

[Poincare]

I don't think it would make sense to split most of this stuff into multiple files because it ends up using some of the instance variables of QueryManager. The fetchQueryOverInterface logic should stay in QueryManager in my opinion.

[stubailo]

Looks good to me, let's merge as soon as CI passes