feat: overhaul settings wizard

[will7200]

1. use projects.change_base_directories instead of internal implementation
2. remove complexity of user interactions when switching to a new data directory, announcing a new project setup with a label instead. Changes are not being made until the user hits saves, so those pop-ups are unnecessary
3. handle case when database file does not exist or table has not been initialized
4. make the wizard float to the top

closes #3

Checklist

• [ ] Keep pull requests small so they can be easily reviewed.
• [ ] Update the documentation, please follow the numpy style guide.
• [ ] Update tests.
• [ ] Categorize the PR by setting a good title and adding one of the labels: bug, feature, ui, change, documentation, breaking, ci as they show up in the changelog.
• [ ] Link this PR to related issues by using closing keywords.
• [ ] Add a milestone to the PR for the intended release.
• [ ] Request a review from another developer.