Make a bindings.h header file with the declarations, so that other projects can reuse the declared structs.

Add parseXMLString overload that supports passing in an MjVFS.

PiperOrigin-RevId: 940579266
Change-Id: I8294988bc4279e80795fab21024f64562a9e6743

wasm/codegen/tests/bindings_diff_test.py

@@ -31,10 +31,13 @@ class BindingsDiffTest(absltest.TestCase):
       self.generated_src = f.read()
     self.template_path_cc = SCRIPT_DIR / 'templates/bindings.cc'
 
-    self.builder = binding_builder.BindingBuilder(self.template_path_cc)
+    self.builder = binding_builder.BindingBuilder()
 
     generator_output = (
-        self.builder.set_enums().set_structs().set_functions().to_string()
+        self.builder.set_enums()
+        .set_structs()
+        .set_functions()
+        .build_string(self.template_path_cc)
     )
     self.assertEqual(
         generator_output,