Refactor: move checks/lib into lib/ to avoid duplicate lib

Lets avoid the mistake of nixpkgs having multiple
libs

checks/flash/flake-module.nix

@@ -56,7 +56,7 @@
     in
     {
       checks = pkgs.lib.mkIf pkgs.stdenv.isLinux {
-        flash = (import ../lib/test-base.nix) {
+        flash = self.clanLib.test.baseTest {
           name = "flash";
           nodes.target = {
             virtualisation.emptyDiskImages = [ 4096 ];