Add Cherry MX kbd switch fp

[perigoso]

See #2416 and #2394

This PR Adds Cherry MX keyboard switch footprints, replacing some existing ones.

[perigoso]

So I had _NoSilk variants of footprints, because some people, including me, don't include silkscreen on the switch footprints for aesthetic reasons, but i was unaware that it was possible to hide it in bulk in pcbnew, so after some digging around and trying things out i came to this:

This is a good versatile solution, and i feel the _NoSilk variants don't make sense given this option, maybe it might not be immediately clear to people but still, any input?

original comment

[perigoso]

Generated footprints with kicad-footprint-generator.

[perigoso]

Re-generated footprints with kicad-footprint-generator after fixups.