Implement collapsible panels for the new room list (#32742)

* Add `react-resizable-panels` library

* Implement a custom SeparatorView

* Add a `LeftResizablePanelView`

* Add a custom `GroupView`

* Export everything from shared-components

* Make it possible to track width/collapse state through settings

* Add a view model to drive the views

* Render views without disrupting the old room list

* Fix lint error

* Disable user interaction on collapsed panel

* Prevent widgets fron hijacking pointer events

* Expand to full width on separator click

* Separator should be shown when focused via keyboard

* Update tests

* Use data-attribute for hover

* Write stories for SeperatorView

* Write vite tests for SeparatorView

* Write tests for LeftResizablePanelView

* More tests

* Fix lint errors

* Fix flakey border on the roomlst

* Fix storybook axe violation

* Update snapshots

* Fix playwright tests

* Fix sonarcloud issues

* Use translated string

* Add better js-doc comments

* Rename `ResizerSnapshot` to `ResizerViewSnapshot`

* Externalize react-resizable-panels

* Link figma designs to stories

* Write playwright tests

* Update screenshots

* Fix lint errors

* Update more screenshots

* Update more screenshots

* Fix flaky toast test

* Update apps/web/playwright/e2e/crypto/toasts.spec.ts

Co-authored-by: Andy Balaam <andy.balaam@matrix.org>

* Fix indentation

---------

Co-authored-by: Andy Balaam <andy.balaam@matrix.org>

apps/web/res/css/structures/_RoomView.pcss

@@ -10,6 +10,12 @@ Please see LICENSE files in the repository root for full details.
     --RoomView_MessageList-padding: 18px;
 }
 
+.mx_LeftPanel_panel {
+    .mx_RoomView_wrapper {
+        height: 100%;
+    }
+}
+
 .mx_RoomView_wrapper {
     display: flex;
     flex-direction: column;