This CL removes FakeBaseEngine and the currently not used functionality
of FakeMediaEngine that depends on it.
Bug: webrtc:9883
Change-Id: I9daa853dedefdf4b4c64b815a7d575eb8ba63c93
Reviewed-on: https://webrtc-review.googlesource.com/c/107581
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25316}