This improves stability and convergence speed of Workbench Temporal AntiAliasing.

This adds a filtering kernel (blackmann-haris, same as EEVEE/Cycles) to the
temporal antialiasing sampling. We also gather neighbor pixels since they might
end up in the pixel footprint.

We use a 1px radius for the filter window which is a bit less than the 1.5 default
of cycles and EEVEE since it does blur quite a bit more than what we have now.

Another improvement is that the filtering is now in log space which improves
AntiAliasing around highlights.

Theses improvement may not be very useful for every day case but it was an
experiment to try to make TAA usable for GPencil.

Test file used :

filtered+logspace	filtered	original