Navigation enhancements: Bottom Navigation, screen transitions, back button

[nahwneeth]

Gist

• Fixed bottom navigation bar.
• Added some default screen transitions.
• Hide back / close button if they do nothing.

Detailed

• Bottom Navigation
  • Split the existing HomeActivity into 2 activities: FeedActivity & HomeActivity.
  • FeedActivity contains the posts list & filters, etc.
  • HomeActivity houses a second NavHost, a NavigationBar & Drawer.
• Screen Transitions
  • Added Accompanist navigation animation as dependency.
  • All the main navigations have a slide in and out transition by default.
  • Removed the fade in and out transitions of the bottom navigation.
• Other enhancements
  • The back button auto hides/shows based on the nav stack state. So opening screens using deep links or the nested screens in the HomeActivity don't have a back button.
  • Community & profiles open as separate screen instead of within the "search" tab.
  • Split up the navigation composables in the MainActivity into separate files.
  • Bottom nav bar opens login screen instead of showing a login toast.

Things to review carefully

• Ensure all deep links and routes have the correct pattern and are working.

Closes

• Closes Screen transition animations #300
• Partly addresses Redirect to login page when required #346

[dessalines]

@twizmwazin @nahwneeth This was a massive change, right in the middle of my autogen_types rework, to prepare for v0.18.0 . I have to revert it, and this change will have to be rebased on that.