Update XML parsing to store asset path so that assets can be recovered and sent to external renderers

PiperOrigin-RevId: 567347908
Change-Id: I4d8e1abe35be3a67643ff925af709921280856f8

src/xml/xml.cc

@@ -321,6 +321,7 @@ mjCModel* mjParseXML(const char* filename, const mjVFS* vfs, char* error, int er
       // this is separate from the Parser to allow multiple URDFs to be loaded.
       model->strippath = true;
       model->fusestatic = true;
+      model->discardvisual = true;
 
       parser.SetModel(model);
       parser.Parse(root);

src/xml/xml_urdf.cc

@@ -87,9 +87,6 @@ void mjXURDF::Parse(
   int id_parent, id_child;
   urPrefix = prefix;
 
-  // set compiler defaults suitable for URDF
-  model->discardvisual = true;
-
   // parse MuJoCo sections (not part of URDF)
   XMLElement* mjc = FindSubElem(root, "mujoco");
   if (mjc) {