Bypass PolySetBuilder for rotate- and linear extrude

[kintel]

PolySetBuilder can in some cases create a non-manifold objects for linear_extrude and rotate_extrude.
Example: rotate_extrude of a 2D object with a single vertex touching the Y axis.
With our new indexed PolySet class, and using the Manifold geometry backend, it should be possible to make these objects proper manifolds and utilize them in CSG operations.

See also #3567

[kintel]

linear_extrude corner case:

linear_extrude(height = 3, scale = [0, 1]) {
  difference() {
    square(2, center = true);
    translate([-0.5,0,0]) square(center = true);
  }
}

Taken from https://github.com/openscad/openscad/blob/master/tests/data/scad/3D/features/linear_extrude-scale-zero-tests.scad

[kintel]

Another linear_extrude corner case:

intersection(){linear_extrude(50,scale=+0.2,convexity=5)circle(d=5,$fn=6);cube(250,true);}

[kintel]

From #4039:

a=110;  // twist, limited to 110 to avoid th strands touching
a2=150; // to set the start point such that the strand would 
        // end on the Z axis if a = 180
h=30;   // height
R=20;   // radius
r=2;    // strand radius

// strand 1
linear_extrude(height=h,convexity=10,twist=a,scale=[0,1])
  translate([R*sin(a2),R*cos(a2),0])circle(r);

// strand 2  
rotate(90,[0,0,1])
  linear_extrude(height=h,convexity=10,twist=a,scale=[0,1])
    translate([R*sin(a2),R*cos(a2),0])circle(r);

Simplified to:

linear_extrude(height=30, scale=[0,1]) circle(2);
cube();

[kintel]

Currently blocked by elalish/manifold#790

Edit: That was a false positive

[kintel]

Status as of 2024-05-01: All known linear_extrude issues fixed by #5096