Revert: tools: add xkbcli-scaffold-new-layout as helper tool

Revert: tools: add xkbcli-scaffold-new-layout as helper tool

While this tool is useful for users starting with a new keyboard layout, it is a
somewhat bad fit for libxkbcommon. It's the only python tool, we don't even
install it yet (because we're not sure yet what it's supposed to do) and there's
a potential for it to expand into more corner cases.

The only tie it has to libxkbcommon is that it templates the data files that
libxkbcommon reads, but those files are effectively public API.

Let's remove this tool from there and instead move it to a separate git
repository where it can go its own way.

This reverts commit d00cf64dbc586a1052e1f0d0e7f1a48bbff293ec