Add audio_engine_tests top-level target

This CL adds a new top-level rtc_test target 'audio_engine_tests'
patterned after 'video_engine_tests'.
It also includes 'channel_receive_unittest' as a dependency of
'audio:audio_tests' and removes 'audio:audio_tests' from
'video_engine_tests'.
The new target is added to the CI configuration.

Bug: None
Change-Id: I3ec308da9fae1a3b6e4b67591d4320c394b2ba23
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/444681
Reviewed-by: Jeremy Leconte <jleconte@google.com>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Auto-Submit: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#46778}