There was a motion towards fill solid/none around
2020 (c.f. b31e97cfeda9b76a165854b98974d253e221e93b),
but it was only for PCB_SHAPE.
Use yes/no universally (solid/none parsing the same way
as currently). In future if there are other fill modes
for these shapes, they can use the same pattern as ZONEs
do now: (fill yes) (hatch etc ....) or similar.
Relates-To: https://gitlab.com/kicad/code/kicad/-/issues/15232
