Add more path lookup tests

[WaVEV]

This increases the test coverage for query refactor (#396).

[timgraham]

What do you mean by "direct query"? The specific importance of these tests isn't clear to me. I'm not opposed to adding them, just trying to understand the motivation of the follow up.

[WaVEV]

What do you mean by "direct query"? The specific importance of these tests isn't clear to me. I'm not opposed to adding them, just trying to understand the motivation of the follow up.

When I say "direct query", that is just a name I came up with to describe the code path that uses a plain match instead of $expr. it’s just how I’ve been referring to that part of the compiler.

When I refactored the $lookup logic in a previous PR, some tests were postponed to be added later. So the motivation here is simply to add unit tests to increase coverage for this “new” way of querying.