Added Aligned Monotonic infill for improving surface finish and clarity of clear parts

[scottmudge]

When following guides like this (https://www.cnckitchen.com/blog/transparent-fdm-3d-prints-are-clearly-stronger) to print clear, solid parts, it's recommended to use zero top and bottom layers, 1 vertical shell, and Aligned Rectilinear infill at 100%.

However, the non-monotonic nature of Aligned Rectilinear means there will potentially be alternating directions of extrusion (although the lines themselves are aligned). This, in my experience, can lead to inferior quality compared to monotonic extrusion patterns.

However, there was no method of using monotonic extrusion patterns in a vertically aligned way. This PR therefore adds an Aligned Monotonic infill pattern.

Using an Aligned Monotonic infill prevents the quality issues of Aligned Rectilinear while preserving the alignment of the extrusion orientation, and improves the general clarity and finish of these solid clear parts. There may be other use-cases as well.

[vovodroid]

I didn't really catch what will be difference between Aligned Rectilinear and Aligned Monotonic? Could you please give some screenshots?

[scottmudge]

It's the same exact difference between Rectilinear and Monotonic. The direction in which isolated "islands" of infill are printed. Rectilinear goes in both directions, depending on which is fastest. Monotonic only puts down infill lines in a single "monotonous" direction.

[staffert]

Is there a way to create a modified monotonic type infill that is +/- 1/2 of an extrusion width offset on each subsequent layer to better fill the voids created by typical Z stacking? This would greatly improve clarity and layer bonding.

[vovodroid]

infill that is +/- 1/2 of an extrusion width offset on each subsequent layer

I have PR with another approach - change extrusion width - Variable perimeters and solid infill extrusion width on even layers. #10429