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*`

libcef/browser/permission_prompt.cc

@@ -154,6 +154,9 @@ class CefPermissionPrompt : public permissions::PermissionPrompt {
       case CEF_PERMISSION_RESULT_IGNORE:
         delegate_->Ignore();
         break;
+      case CEF_PERMISSION_RESULT_NUM_VALUES:
+        DCHECK(false);
+        return;
     }
   }