Clean every window and add the results into the region grids

[KurbyDoo]

Background

This ties the other three sub tickets together and is the point where the sampler actually produces a region.

Description

For each window position, cut the window out of the noise canvas, hand it to #23, then add the returned patch into the region grids at that same position using the weight grid from #33. Once every window has been added, read the finished grid back out and return it.

Take two things as arguments rather than building them in here:

• a function that takes a patch and returns a cleaned patch
• the region grids from Terrain Store #31

Take a function rather than the whole pipeline object. Cleaning a patch is the only thing needed from #23, so asking for only that is enough, and a test can then pass an ordinary function instead of building a fake class.

Do not take the tile cache. This never touches finished tiles.

Testing, passing a function that ignores its input and returns a patch of all fives:

• Assert the finished grid is all fives everywhere, including the overlaps and the corners. If the overlaps read higher then the weights are not being divided out
• Assert the finished grid is the region's full resolution size
• Assert the function was called once per window position and no more
• Assert the same seed and region run twice give identical grids