Create new meta-qt6 layer

The current yocto meta layer for Qt 5 is meta-qt5, available in upstream (https://github.com/meta-qt5/meta-qt5) and maintained outside of TQC. The name alone makes it unsuitable for Qt 6 content, making in necessary to create new meta-qt6 layer. The change to cmake build system also makes existing recipes no longer suitable.

Current the contributions to meta-qt5 layer can be roughly divided into two categories: updates to Qt modules and fixes needed to work against latest Yocto releases.

We have done most of the Qt module update changes while making sure meta-qt5 works with latest yocto has been done by the opensource maintainers.

The question is how much extra work do we need to do ourselves, if we take on the full maintenance of meta-6 and keep it in Qt's codereview.

We also need decide which license will be used with the meta-qt6 layer. Majority of meta layers follow MIT licensing including meta-qt5, while meta-boot2qt is using GPL|commercial licensing.