Add Tab bar (EXPOSUREAPP-4639) (#2235)

* Add bottom bar

* Fix di

* Adjust theme

* Align content on top of bottom bar

* Enhance findNavController

* Adjust Bottom Bar

* Remove diary card

* Remove up button

* lint

* Adapt MD theme

* Fix ui tests

* Delete contact diary , handle onboarding

* Remove x button

* Show bottom nav only for Home and contact diary destinations

* Only contact diary overview screen

* Adjust alert dialog theme

* update docs

* Fix close button issue

* Revert close button changes

* Rename text resources

* Make visibility logic flexible for future additions

* Fix typo

* Contact diary onboarding's bottom bar behaviour

* Update ContactDiaryOnboardingFragmentTest.kt

* Update Corona-Warn-App/src/main/res/values/strings.xml

Co-authored-by: Sabine Loss <44154356+SabineLoss@users.noreply.github.com>

* Update contact_diary_overview_fragment.xml

* Small refactoring

* Remove un required gravity

* Use accent colour

* Move diary settings into vm

* Update MainActivityViewModelTest.kt

* Fix styling in bottom sheet dialog

Co-authored-by: Sabine Loss <44154356+SabineLoss@users.noreply.github.com>
Co-authored-by: harambasicluka <64483219+harambasicluka@users.noreply.github.com>