Smaller handle width, small shadow on the top of the show more button if there's more rooms to be shown. The resize handle also only shows when you're hovering in the area now.
The original design called for the shadow to show up only if the user is cutting a tile or dragging, however that is complicated implementation-wise. For speed and encouraging a dogfooding pattern we're going ahead with this behaviour instead.
When the user would click 'show more' they would be presented with a 'show less' button that occluded the last room.
Similarly, if they resized the list so that all their rooms would be shown and refreshed the page, they would find their last room covered by the button.
This changes the handling so that showAllClick() sets the height to numTiles + button padding, and adjusts the height calculations on render to deal with relative tiles.
This also removes the conditional padding of the resize handle, as we always occupy the 4px of space. It was leading to rooms getting trimmed slightly by the show N button.
The 'sort by' radio buttons are blocked by https://github.com/matrix-org/matrix-react-sdk/pull/4731 as it contains the styles needed.
The 'unread rooms' checkbox is intentionally not hooked up. This is a more complicated refactoring that needs to be done.
The message preview checkbox works, though the previews remain hardcoded in this change. The primary intent of this change is to have a good enough context menu and the hover states.
The hover states are as described in the design.
