Convert planar faces to polygonal representations with inner loops

For the sake of 2D nesting we need realistic 2-dimensional parts with optional inner loops. Mobius (www.openmobius.org) comes with a JSON format that has to be respected. Here is one example:

{
  "name": "a",
  "outerPolygon": [[0, 0], [1, 0], [1, 1], [0, 1]],
  "innerPolygons": {
    "i0": [[0.25, 0.25], [0.35, 0.25], [0.35, 0.75], [0.25, 0.75]],
    "i1": [[0.45, 0.25], [0.75, 0.25], [0.75, 0.75], [0.45, 0.75]]
  },
  "count": 1,
  "angleStepDeg": 15
}

The properties count and angleStepDeg can be initialized with reasonsble defaults, e.g. 1 and 15 respectively.

There is already a similar function named misc-convert-curves-poly (https://analysissitus.org/commands.html#misc-convert-curves-poly, see also #326 (closed)) that works on a single wire (contour). Let's introduce another command named misc-convert-face-poly that would work as follows:

If a face ID is provided, it uses the passed ID of the target face to convert.
If no face ID is provided, the currently selected face is taken from the viewer.
If a filename is provided, the dump is serialized to the specified file.
If no filename is provided, the dump is rendered in the JSON UI dialog as we usually do.

The discretization can be taken from the facets of the target face. If a face hasn't been meshed, the facets should be automatically generated with autoselected precision values.