Most system includes for CoroutineTests.cpp should be moved to GraphQLService.h

[wravery]

I implemented the original version of await_worker_queue in the unit test implementation and update the system headers there:

#include <condition_variable>
#include <mutex>
#include <queue>
#include <thread>

Then I realized I could generalize it and it would be useful along with await_worker_thread, so I moved it to GraphQLService.*, but I forgot to transfer the system headers like <condition_variable>. It still works on each platform I'm targeting in the CI build or on my machine, but it makes the code less portable if I depend on another system header's implementation to pull in all of the std types I'm using.