This diff introduces refactoring the Tonic client names for the Identity service in a Rust native library to the Client -> IdentityClient.
As we are using a single Rust library for the native which will contain clients and helper functions for all services we should refactor the Identity service-related function names to be more specific.
After this, we can add new clients for other services e.g. TunnelbrokerClient.
Linear task: ENG-1333