* We retain the behavior from legacy sidebar which re-opens the previously open sidebar panel when the sidebar is toggled open * Rename SidebarState's '#previousLauncherVisible' to '#previousLauncherExpanded' as it actually tracks expandedness * Don't persist the panel/command id when the panel isn't open * Ensure all the sidebar tests reset the sidebar state when they are done Differential Revision: https://phabricator.services.mozilla.com/D234773