ITS: update tools/dng_noise_model.py with improvements

Use rawStats instead of raw captures to speed things up.
Use a smaller tile size to reduce low freq image changes
Increase exposure bracketing stops from 4 to 8

Minor gpylint cleanups for alignment and spacing.

bug: 158028170
Change-Id: I6e2007bb8f350071b719af68a051858dc7c80af1
1 file changed