See https://github.com/flathub/flathub/wiki/AppData-Guidelines#icons-and-categories

This should users get accustomed to the UI changes we plan for 1.3

Also it hides the problems with the not scrollable tabs list because much more tabs fit the window

- Always show new avatars with status
- Remove tabs advanced config options
- Increase tabs width

- Use Header capitalization https://developer.gnome.org/hig/stable/writing-style.html.en#capitalization
- Use ellipsis whenever an action needs more user input

Fixes #10073

Fixes #10080

Start of 1.3 development cycle

Fixes #10077

CSSConfig now generates classes for account colors at start so
we can use them later easily