Improve GitLab UI by adding project avatar dropdown with open source icons

Proposal

There is a number of Open Source icon sets with a permissive license. For example:

• https://icons.getbootstrap.com/
• https://octicons-git-v2-primer.vercel.app/octicons/
• https://fontawesome.com/

The alternative to the icon sets are emoji.

Would be useful to have the ability to quickly select an icon from the dropdown in GitLab Project general settings "Project avatar" in addition to the already existing upload feature.