[schema] Add schema query tests, inference fixes

[stefanprobst]

This is for #11480

Adds:

• more query tests
• test for merging inferred field types
• some test todos
• added JSdoc

Fixes:

• ensure schema composer has Node interface
• make noDefaultResolvers: true mean addDefaultResolvers: false
• rebuild with SitePage context now works correctly. A more general solution for on-demand schema rebuild would still require a bit more work.
• merging nested types in inference: because we now guarantee priority when we have conflicting field names, we have to deal with temporary TypeComposers on nested fields. Also ensure that we honor array depth; and get the nested TC's name from an existing TC, not from createSelector.
• make sorting work (lowercase sort order enum) -- this has triggered another Loki mismatch (it is the same issue with null values on indexed fields: the kitchen sink query sorts DESC on likes, which sorts nulls to the front, and those screw things up. It is good that we know this, and we should find a solution, but it's an edge case. The easiest "fix" for now would be to adjust sort order in kitchen sink query from DESC to ASC and update the snapshot. EDIT: I now did just that.

[freiksenet]

LGTM, do you want to add TODO tests on this branch or separately? Anyway, you can merge it if you want.