AbstractTransportTest's fakes should be factored out and made available to other tests

[jdcormie]

Is your feature request related to a problem?

Many grpc-java unit tests create their own fake implementations of the various listener interfaces for synchronization. This results in code duplication, and low quality one-off implementations. When a test fails, both the system-under-test and the test itself are suspect.

Describe the solution you'd like

High quality fake implementations of ServerListener, ServerTransportListener, ServerStreamListener and ClientStreamListener, available for other unit tests to use, and each with their own unit tests.

Describe alternatives you've considered

status quo?

Additional context

https://github.com/grpc/grpc-java/pull/10822#discussion_r1458031851