Audio recording enhacement

[nishant-sg]

Before: The user could only record for a fix 5 seconds

After: As long as the user is talking everything will be recorded. When the user stops talking it will take a three seconds to stop recording.

Print statements have been removed, for demo purpose please look at the video

https://github.com/ArduPilot/MAVProxy/assets/70840360/66e6ed42-117b-4a0e-882d-eef84e6a5316