Improved visual quality with 3x times speed-up.
Change list:
1. Remove second chance filter in temporal denoising filter to mitigate trailing artifact.
2. Add swap buffer to save one whole-frame memcpy.
3. Do noise estimation on every N blocks.
4. Adopt a faster moving object detection algorithm (change the structure).
5. Refactor the for loops and PositionCheck().
6. Refactor the function ReduceFalseDetection (RFD).
7. Fix a bug in TrailingBlock() which causes a mismatch.
8. Change unit test to support swap buffer test.
9. Remove CopyMem8x8, use memcpy to copy U/V plane which can be optimized future.
10. Remove DenoiseMetrics.
Review URL: https://codereview.webrtc.org/1871853003
Cr-Commit-Position: refs/heads/master@{#12340}
afaae0d151