Consider switch to Andrew Ellis more compact test pattern

[garethky]

References:
https://github.com/AndrewEllis93/Pressure_Linear_Advance_Tool
https://ellis3dp.com/Print-Tuning-Guide/articles/pressure_linear_advance/introduction.html

Pros:

• Numbers are backed by a layer so removal is much cleaner, would solve Connect numbers and pattern to make print removal easier #8
• More compact, doesn't require as large of a print area, likely solves Automatically shink the size of the test pattern for small printers #9
• Directly observe corner performance

Cons:

• Its 2 layers, takes longer to print
• Corner issues may not be as easy to see as a straight lines

[Gefionious]

I actually really like the idea of the corner; that is almost always where my issues seem to show up the most, not in straight lines. Thank you for all your work on this, I am going to try your method tomorrow, I have been having some under extrusion issues and I think they might be related to pressure advance.