Group and sorting improvements

Problem/Motivation

Discussed today in UI Suite monthly meeting.

Ensure consistency across UI Suite ecosystem.

Proposed resolution

Now that groups had been introduced:
- Introduce a weight property to styles
- Form: sort groups alphabetically
- Form: inside group sort styles by weight then alphabetically
- Form: place styles without groups in a "Other" group
- Form: if there is only the "Other" group, remove the group and place styles directly in the UI Styles fieldset
- Styles library: Regroup styles by group, sort by weight then alphabetically in a group, sort groups alphabetically

Need to create a change record regarding groups in styles library.