Improve team manegement UX for member removal and role change

[aerosol]

Changes

This fixes various issues within team management scope:

• prompts the user with a confirmation dialog before demoting their own role
• prompts the user with a confirmation dialog before removing any member entry
• redirects to team general settings in case the user demoted their own role to either billing, editor or viewer
• redirects to /sites with no team identifier in case the user removed themselves from the team

Tests

• Automated tests have been added
• This PR does not require tests

Changelog

• Entry has been added to changelog
• This PR does not make a user-facing change

Documentation

• Docs have been updated
• This change does not need a documentation update

Dark mode

• The UI has been tested both in dark and light mode
• This PR does not change the UI