* feat: upgrade react router to v6
* fix: all test cases affected by react router upgrade
* refactor: fix navigations
* fix: test cases affectewd due to lib-special-exams
* refactor: improve code coverage
* Updating Dropdown and Button.
* Fixing broken tests and test warnings.
* Remove comment block.
* Using variant=“link” on the Tabs Dropdown.Toggle.
* Fixing some merge conflicts.