DocumentSourceChangeStream::createFromBson() currently can make a network roundtrip to the config server to fetch the placement history status for v2 change stream readers on the router. This code is currently called once per change stream setup on the router.

SERVER-115078 introduces some changes that can make the createFromBson() code be executed multiple times during setup, which could result in multiple network roundtrips.

Also createFromBson() can be called when running the $queryStats stage, which would also make an undesired network roundtrip.

As a result, the code in DocumentSourceChangeStream::createFromBson() should be adjusted so that we don't want to do anything expensive while parsing. The function should be as cheap as possible and have minimal/no side-effects.