Reduce specificity of `rtl`, `ltr`, and `dark` variants (when using `darkMode: 'class'`) to make them the same as other variants. This also sorts the LTR/RTL and dark variants later in the variant plugin list to ensure that the reduced specificity doesn't cause them to start "losing" to other variants to keep things as backwards compatible as possible.

Resolves a long-standing issue where `darkMode: 'media'` and `darkMode: 'class'` had different specificity, which meant switching your dark mode strategy could break your site.