Move audio- and video-specific utilities to audio_test_common (newly added target) and video_test_common. Bug: webrtc:10198 Change-Id: Ia10fa5c0a51d9b1f37db4964984d22fc5b269bb1 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/268980 Commit-Queue: Niels Moller <nisse@webrtc.org> Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org> Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org> Auto-Submit: Niels Moller <nisse@webrtc.org> Cr-Commit-Position: refs/heads/main@{#37570}