Support film grain application whose only effect is clipping to video range

This is the parameter combination:
num_y_points == 0 && num_cb_points == 0 && num_cr_points == 0 &&
chroma_scaling_from_luma == 1 && clip_to_restricted_range == 1

Film grain application has two effects: adding noise, and optionally
clipping to video range

For luma, the spec skips film grain application if there's no noise
(num_y_points == 0), but for chroma, it's only skipped if there's no
chroma noise *and* chroma_scaling_from_luma is false

This means it's possible for there to be no noise (num_*_points = 0), but
if clip_to_restricted_range is true then chroma pixels can be clipped to
video range, if chroma_scaling_from_luma is true. Luma pixels, however,
aren't clipped to video range unless there's noise to apply.
dav1d currently skips applying film grain entirely if there is no noise,
regardless of the secondary clipping.