`AudioProcessingImpl::ApplyConfig()` is deprecated, instead this CL uses `AudioProcessingBuilderForTesting::SetConfig()`. Also includes code style improvements. Bug: webrtc:5298 Change-Id: Id6790bd110f2eb87deafa851f5c83c3fd00692b9 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/235376 Commit-Queue: Alessio Bazzica <alessiob@webrtc.org> Reviewed-by: Per Åhgren <peah@webrtc.org> Cr-Commit-Position: refs/heads/main@{#35288}