Use a dedicated function for wrapper struct names

This change introduces a `wrapper_struct_name` function in `structs.py` to consistently generate the name of the C++ wrapper struct from a C struct name. All call sites in `functions.py` and `structs.py` that previously used `common.capitalize` for this purpose now call `wrapper_struct_name`.

PiperOrigin-RevId: 837544242
Change-Id: Ibe5fea8294283dae63bb8d064fd8beb8cfd3f2fe

wasm/codegen/templates/bindings.cc

@@ -386,7 +386,7 @@ MjSpec::~MjSpec() {
 mjSpec *MjSpec::get() const { return ptr_; }
 void MjSpec::set(mjSpec *ptr) { ptr_ = ptr; }
 
-std::unique_ptr<MjModel> loadFromXML_wrapper(std::string filename) {
+std::unique_ptr<MjModel> mj_loadXML_wrapper(std::string filename) {
   char error[1000];
   mjModel *model = mj_loadXML(filename.c_str(), nullptr, error, sizeof(error));
   if (!model) {