* Refactor shouldUpdateScroll passing

So far, shouldUpdateScroll has been manually passed down from the very top of
the React component hierarchy even though it is a static function common to
all ScrollContainer instances, so replaced that with a custom class extending
ScrollContainer.

* Generalize “press back to close modal” to any modal and to public pages

* Fix boost confirmation modal closing media modal

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

* Freeze scroll position when a dropdown menu is open in the TL

* Apply this to direct TL as well

* Fix case when mouse leaves the menu

* Make the area to the left “Show Thread” also expand the toot in Web UI

* Clicking the left part of a conversation with the avatars now opens it in Web UI

Fix #11414, fix #9860, fix #10434

Fix #9097

Fix #9096

* Add conversations API

* Add web UI for conversations

* Add test for conversations API

* Add tests for ConversationAccount

* Improve web UI

* Rename ConversationAccount to AccountConversation

* Remove conversations on block and mute

* Change last_status_id to be a denormalization of status_ids

* Add optimistic locking

* Action/reducer for changing column settings takes a path and a value
instead of a javascript object

* Settings menu version and column headline version working simultaneously

* remove column headline entirely

* remove css for headlines that aren't possible now

* Remove commented out code from unfruitful attempt at this feature

* Give direct timeline its own column settings bc it doesn't have a media only option

* Fix typo in public timeline code that was preventing per-column settings from working properly

* Fix codeclimate issues

* Missing semicolons

* Use redux state to set onlyMedia, let that do the update instead of a callback. Consequently, unpinned setting works without history modification

* Unused import