Adds QA checks to copper sliver tests. Adds the following checks:
- Dot product between two arms (quickly avoids checks for >90°)
- Checks the sliver is convex (area test)
- Eliminates minor slivers with angles that are approximately 0 and ones
with the opposite side width beneath a configurable level
- Updates Clipper2 to fix a couple of jagged edges on inflate
- Adds simplify during zone fill inflation to limit jaggies
Fixes https://gitlab.com/kicad/code/kicad/issues/14549
f7f52d77e4