mkosi: Update to latest

- Drop Netdev= as it was removed in mkosi
- Always install python-psutil in the final image (required for networkd tests)
- Always Install python-pytest in the final image (required for ukify tests)
- Use the narrow glob for all centos python packages
- Drop the networkd mkosi config files (the default image can be used instead)
- Use ".conf" as the mkosi config file suffix everywhere
- Copy src/ to /root/src in the final image and set gdb substitute path in
  .gdbinit to make gdb work properly

.gitignore

@@ -31,11 +31,10 @@ __pycache__/
 /.mkosi-*
 /mkosi.builddir/
 /mkosi.output/
-/mkosi.default
 /mkosi.installdir/
 /mkosi.secure-boot.*
 # Ignore any mkosi config files with "local" in the name
-/mkosi.default.d/**/*local*.conf
+/mkosi.conf.d/**/*local*.conf
 /tags
 .dir-locals-2.el
 .vscode/