Add Quick Links to the Project Tree

[vkbo]

Summary:

This PR adds a tool button to the Project Tree toolbar with a dropdown menu with links to each of the project's root folders. Clicking one will change the selected item to the root folder and scroll it into view. The menu can be activated with the keyboard shortcut Ctrl+L.

Related Issue(s):

Closes #1137

Reviewer's Checklist:

• The header of all files contain a reference to the repository license
• The overall test coverage is increased or remains the same as before
• All tests are passing
• All flake8 checks are passing and the style guide is followed
• Documentation (as docstrings) is complete and understandable
• Only files that have been actively changed are committed