Move GObject / GLib into Runtime folder

[badcel]

Move GObject / GLib into a new Runtime folder.

The code in GObject / GLib will be mostly written by hand as it is the foundation code to allow bindings and acts as some kind of runtime.

The remaining projects int he Libs folder will be as much autogenerated as possible.

This depends on #134 as there are some cleanups regarding csproj files which allow to avoid duplicated csproj code (General.props and Nuget.props).

[badcel]

I'm not sure if we need the split. We need to see if there is a difference in generating the code for GObject / GLib compared to other projects. This depends on #100