Partial revert "Convert phases that contain ":" to dont* = true"

This reverts commit dc48d23a0f.

This deactivated custom build phases in many vim plugins overrides.
Also we could change our overrides it may break out-of-tree usage.

pkgs/misc/vim-plugins/build-vim-plugin.nix

@@ -54,7 +54,8 @@ rec {
     }));
 
   buildVimPluginFrom2Nix = attrs: buildVimPlugin ({
-    dontBuild = true;
-    dontConfigure = true;
+    # vim plugins may override this
+    buildPhase = ":";
+    configurePhase =":";
   } // attrs);
 }