kde_projects: Locate KDE projects post-Gitlab migration.

• kde-build-metadata has moved, update our pre-baked module to request the right name.
• Enable the invent.kde.org logic by default.
• Use invent.kde.org instead of anongit.kde.org for kde: fetch URL

kdesrc-build still makes a lot of complaints about having to move git
remotes for some reason but at least I can make it through part of a
build.