Show enum members as defined order(sort via its value)

[taozuhong]

Describe the bug
Sometimes, I need to get the enum member value for using in other languages, now it's showing as member name alphabet order, so I can't get the correct member value.

To Reproduce
Steps to reproduce the behavior:

1. Go to page: https://valadoc.org/gtk4/Gtk.IconSize.html

Expected behavior

1. Show enum members as defined order(sort via its value) on the left tree and content page
2. show its value on the content page.

Screenshots