[WIP] User list section/filters

[srdeotarse]

What does this PR do? This WIP PR migrates earlier struture of RightColumnView in views.py to structure similar to LeftColumnView with toggling between StreamsView and TopicsView. This PR mainly intends to add new RecipientsView that displays recipients of the current narrow(All_messages, PMs, Streams, Topics etc) in the right column.

This fixes #575

CZO - https://chat.zulip.org/#narrow/stream/206-zulip-terminal/topic/User.20list.20sections.2Ffilters.20.23T575 Tested?

• [ ] Manually
• [ ] Existing tests (adapted, if necessary)
• [ ] New tests added (for any new behavior)
• [ ] Passed linting & tests (each commit)

Commit flow

Notes & Questions

This WIP PR only includes transition from earlier structure of RightColumnView to new structure based on LeftColumnView structure. It includes modifications to UserView Interactions

This PR is motivated by PR #459 Visual changes

[neiljp]

@srdeotarse We discussed this in the stream, so I'm marking it as awaiting update on the assumption that we've clarified how to move forward with this. Let me know if you need more feedback/review.

[zulipbot]

Heads up @srdeotarse, we just merged some commits that conflict with the changes you made in this pull request! You can review this repository's recent commits to see where the conflicts occur. Please rebase your feature branch against the upstream/main branch and resolve your pull request's merge conflicts accordingly.