Support more complex data in QueryString coercion

[slifty]

Our new QueryString coercion will coerce root level values and basic values contained in the first layer of an array.

This means it does NOT coerce to the full potential levels as outlined in https://github.com/DefinitelyTyped/DefinitelyTyped/blob/ab8d5e1916112f343d02c5652dadee232b5deaa3/types/qs/index.d.ts#L73

Specifically:

• Arrays of depth >1 (e.g. [["42"]])
• Objects (e.g. { foo: "42" })

This is a limitation of the implementation and an unexpected one. We don't need this today, since there are no APIs that involve this kind of complex queryString, but it is tech debt that we'd have to pay off the moment we do.