This patch rewrites and optimizes the Double Edge Mask node to be orders
of magnitude faster. For a 1k complex mask, it is 650x faster, while for
a 1k simple mask, it is only 50x faster.
This improvement is attributed to the use of a new Jump Flooding
algorithm as well as multi-threading, matching the GPU implementation.
The result of the new implementation differs in that the boundaries of
the masks are now identified as the last pixels inside the mask.
Pull Request: https://projects.blender.org/blender/blender/pulls/117545
