rename gamedev-framework into gf-gamedev-framework

[jube]

The package can also be named gf and the split rule now renames it gf-gamedev-framework instead of simply gamedev-framework, creating two project pages. This rename merge the gamedev-framework package into gf-gamedev-framework.

[AMDmi3]

Your fix won't work as there's no gf-gamedev-framework at 800xx rule, because it's introduced in 850xx rule when gf is split. So instead, merge gamedev-framework into gf so all packages end up in the same project, and later split it into gamedev-framework, reusing the name used in vcpkg.