Add NUM_VALUES for enums and size for structs (see #3836)

API versioning requires that enumerations end with a count value
(`*_NUM_VALUES`) and structs begin with a size value (`size_t size`).
Wrapper templates are updated to support structs with different size
values indicating different versions.

To test:
Run `ceftests --gtest_filter=ApiVersionTest.StructVersion*`

tests/cefclient/browser/task_manager_test.cc

@@ -45,6 +45,9 @@ std::string TaskTypeToString(cef_task_type_t type) {
       return "Shared Worker";
     case CEF_TASK_TYPE_SERVICE_WORKER:
       return "Service Worker";
+    case CEF_TASK_TYPE_NUM_VALUES:
+      NOTREACHED();
+      break;
   }
   return "Unknown";
 }