R1:a42ec32c98b6

Modify the Aphlict client to use `LocalConnection`.

Summary:
Ref T4324. Currently, an Aphlict client (with a corresponding connection to the Aphlict Server) is created for every tab that a user has open. This significantly affects the scalability of Aphlict as a service. Instead, we can use `LocalConnection` instances to coordinate the communication of multiple Aphlict clients to the server.

Similar functionality existed prior to D2704, but was removed as the author was not able to get this functionality…