Fuzzes the config and audio inputs to GainControlImpl.
Seems able to cover a few hundred lines of code that the APM fuzzer hasn't been able to reach.
Bug: webrtc:9413
Change-Id: I32776505be9c416ec03113c12437a92dcfadd827
Reviewed-on: https://webrtc-review.googlesource.com/84589
Commit-Queue: Sam Zackrisson <saza@webrtc.org>
Reviewed-by: Alex Loiko <aleloi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23709}