Implement collapsible panels for the new room list

[MidhunSureshR]

For https://github.com/element-hq/wat-internal/issues/292

This PR implements collapsible left panel using react-resizable-panels:

• Three views are introduced (GroupView, LeftResizablePanelView and SeparatorView) along with a ResizerViewModel to implement the custom behaviour we need.
• The old room-list and its separator are unaffected.

I've spent a considerable amount of time trying to match the new implementation with the existing one so that we wouldn't need to update all the playwright screenshots. But this just isn't possible due to the library setting fractional widths (like 370.4px) and differences between headed and headless mode in playwright.

[daniellekirkwood]

i think you can tab through the contents of the left-panel when it's closed before it gives you the option to open the left panel which doesn't feel right? @MidhunSureshR happy to screensrecord/shreenshare :)

[daniellekirkwood]

when on a call, i can't click and drag to open the left panel -- i can only click to snap open

[daniellekirkwood]

it appears the drag function is not easy to use in a call ...

[gaelledel]

Observations

1. The separator line seems thicker as soon as you hover/interact with it. When clicking away on the UI, the line returns to its original thickness. We should not see any thickness difference and we should just preserve the default thickness at all times.

2. When you enter focus mode, there is an extra line on top of existing ones

3. When reaching S size, it "feels blocked". As a user you really have to push hard in order to access the full collapsed view. This will be detrimental as the collapsed view will be harder for user to discover. It just also simply feels hard to get the collapsed view.

4. When reducing from S size to full collapsed, it seems there is a "bounce" like animation. Ideally, we'd need to remove this bounce to ensure the closing feel to be natural and smooth.

5. When fully collapsed, the OnClick interaction should expand to full view. Currently, it expands to S view. This happens if user has stayed on S view prior to reaching collapsed view

6. When in a call, ideal behaviour would be for the room list to "auto collapse" and when you exit, the RL should return to the size set previous to the call.

7. During calls, it seems impossible to reach the full collapsed view

[daniellekirkwood]

i also can't appear to make the left panel wider when i'm in a call

[andybalaam]

Looks ok from a crypto point of view.