Complete manual testing for undeclared fields

[varungandhi-src]

• Manually test Go to Def and Find References when an undeclared field is present in different files. (Currently, this will create two different SymbolInformation values for the same symbol in different files.)
• Manually test an inheritance hierarchy involving multiple classes. In that situation, it seems like the transitive linkage should be happening through relation traversal. E.g. if C < B < A then C.@f would be defined by B.@f which would be defined by A.@f. In that case, we should check if all references to A.@f show up when we do Find references on C.@f. There is a TODO related to this, which should be updated/removed.

Follow up from #116, hoping to get https://github.com/sourcegraph/sourcegraph/issues/42499 resolved first.