Updating to `react-router` v6.

[dennisoelkers]

Description

Motivation and Context

This PR is preparing the update to react-router v6. Notable changes include:

• Switch has become Routes
• Only Route components are allowed below Routes
• history access should be avoided, instead we can use useNavigation
• Prompt is not present anymore

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Refactoring (non-breaking change)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.