[5.1.0] Use icons

Problem/Motivation

In #3467605: Add Bootstrap icons, we declared the Icons in UI Suite Bootstrap.

Now let's use the breaking change of 5.1.x to also make UI Icons a requirement and to use icons automatically in UI Suite Bootstrap to improve the UI out-of-the-box.

Proposed resolution

Add UI Icons in the theme dependencies.

Maybe add a hook_requirements inspired by https://gitlab.com/ui-icons/ui-icons-example/-/blob/main/ui_icons_bootst...

• #3466028: Ensure media library popin is usable: media library grid/table links
• #3466028: Ensure media library popin is usable: media library remove button To update with new API
• search block submit button Done with autoiconize
• Bootstrap 3 inspired auto iconized submit button
• Local action links
• Commerce: cart icon
• File: file icon
• File/image widget ? keep it as it is
• Autocomplete/ajax input: #3406539: [BS3 port] Autocomplete
• Status messages? https://getbootstrap.com/docs/5.3/components/alerts/#icons, by default status messages are displayed with JS, and as JS is not linked to UI Suite, we don't want to hardcode the icons in JS
• Table: sort icons
• RSS feed
• About text formats
• Other?

Also proper theming for the icon selector widget.

https://getbootstrap.com/docs/5.3/helpers/icon-link/