Isolates the build targets for the `AdaptiveDigitalGainController` dependencies that will be moved into `GainController2`. `AdaptiveDigitalGainController` will be removed because the wrapper itself adds little - that's the reason why it has no unit tests. Bug: webrtc:7494 Change-Id: I2ca41f9255c8faefe4b2cb4ec1f8db536e582f39 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/280482 Reviewed-by: Hanna Silen <silen@webrtc.org> Commit-Queue: Alessio Bazzica <alessiob@webrtc.org> Cr-Commit-Position: refs/heads/main@{#38799}