* Replace operation semaphore with shared behavior source

Replace the client's counting of active operations with a
single, shared operation result source in a Map. This achieves
the same semaphore behaviour but replaces it with a binary
semaphore-like cache, where the cached source remembers the
last active result.

* Prevent emitting cached result if a new result emitted first

* Reuse client.query() in client.readQuery()

* Add tests for shared source behaviour

* Abstract replay logic in Client

* Add test for shared subscription behaviour

* Fix linting issues