Add GetStats to AudioInput in Android ADM

This CL adds a GetStats method to the AudioInput interface in the
Android AudioDeviceModule, and updates
AndroidAudioDeviceModule::GetStats to combine stats from both input and
output.

Bug: b/384830998
Change-Id: I36c00c1d56de2ed67ad4531d2006a18c205d6f99
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/466900
Reviewed-by: Per Åhgren <peah@webrtc.org>
Reviewed-by: Henrik Andreassson <henrika@webrtc.org>
Commit-Queue: Viktor Grönroos <wilhelmsson@google.com>
Reviewed-by: Jakob Ivarsson‎ <jakobi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#47612}