TestRTC: Improve mic test by adding fail criteria based on input volume and also active input channel detection.

Added testing of input channels to determine how many are active and display the volume.
Added validation of the input volume, if its too low fail the test.
I tried using 0 which results on 2048 on Linux and Windows, however on Windows it does not have time to capture any data, just noticed even 4096 is not enough on Windows, changed it too 8192.