Support Apple Silicon on macOS

This builds on work by @sephamorr and others to support Apple Silicon on macOS. It has been tested against updated versions of kicad-mac-builder (kicad/packaging/kicad-mac-builder!376 (merged)) and dyldstyle (https://gitlab.com/kicad/packaging/kicad-mac-builder/-/merge_requests/376#:~:text=kicad%20and%20dyldstyle%20(-,adamwwolf/dyldstyle!4,-).). You can see builds on builder.wayneandlayne.com, like https://builder.wayneandlayne.com/job/kicad-universal/50/. There are signed and notarized builds in the SigningAndNotarization directory for folks with access.

Folks should not need dyldstyle/wrangle-bundle for local builds at all anymore, even with Python and all the accoutrement, just redistributable builds--and that's still gonna be fixed and dyldstyle is going to completely go away, just not today.

This adds a top-level directory, signing/. I don't think I particularly like that? Suggestions on where to put the applicable CMake files are greatly appreciated (or feel free to just make the change, I don't mind at all)

Additionally, this removes the bundled in-tree copies of BundleUtilities. They weren't being used everywhere, and they're not needed for macOS bundling anymore. The changes we backported are in all the versions Mac folks will be on anyway.

Thanks, folks! If there are any changes needed, you can let me know and I'll do them quick or feel free to make them.