Now that the code is in C++, quite some duplication between "byte" and
"float" effect code paths can be reduced (easier than it was in C times).
So I did that, removing about 400 lines of code.
In that process I accidentally made Gaussian Blur faster, since while
reducing the amount of code I noticed it was doing some things
sub-optimally (calculated kernel tables for each job, etc.). Applying
100x100 gaussian blur on 4K UHD resolution image strip on Ryzen 5950X
went 630ms -> 450ms.
Pull Request: https://projects.blender.org/blender/blender/pulls/116089
5cac8e2bb4