Rename EnableDenosing --> EnableDenoising. Delete VideoProcessing FrameStats methods. Delete VideoProcessingImpl::BrightnessDetection and related files. Delete VideoProcessingImpl::Deflickering and related files. Delete VideoProcessing::Brighten. BUG= Review URL: https://codereview.webrtc.org/1901393003 Cr-Commit-Position: refs/heads/master@{#12521}