Add an introspect module for structs.

Also missing struct fields to the Python bindings that were discovered as a result of the new `introspect` metadata.

PiperOrigin-RevId: 523947396
Change-Id: I367fd2dc8d5fd7e5712a45b70a5c50da51d152e4

python/mujoco/render.cc

@@ -214,6 +214,7 @@ PYBIND11_MODULE(_render, pymodule) {
   X(windowStereo);
   X(windowDoublebuffer);
   X(currentBuffer);
+  X(readPixelFormat);
 #undef X
 
 #define X(var)                      \

python/mujoco/structs.cc

@@ -23,10 +23,8 @@
 #include <ios>
 #include <iostream>
 #include <memory>
-#include <numeric>
 #include <optional>
 #include <sstream>
-#include <stdexcept>
 #include <string>
 #include <string_view>
 #include <type_traits>
@@ -2167,6 +2165,7 @@ This is useful for example when the MJB is not available as a file on disk.)"));
       })
   X(maxgeom);
   X(ngeom);
+  X(nskin);
   X(nlight);
   X(enabletransform);
   X(scale);
@@ -2228,6 +2227,7 @@ This is useful for example when the MJB is not available as a file on disk.)"));
   X(textrgb);
   X(linergb);
   X(range);
+  X(highlight);
   X(linepnt);
   X(linedata);
   X(xaxispixel);