Checkmk Werk 15071: UI: Introduce new toggle icon

ID: 15071 Title: UI: Introduce new toggle icon Component: Multisite Level: 1 Class: New feature Version: 2.2.0i1 Page menu entries which toggle certain view parameters, e.g. "Show checkboxes" in the "All hosts" view, used to show a checkbox icon, that was either empty or checked. For a more intuitive, consistent and visually understandable user experience, a new toggle icon is introduced and the text of such entries is toggled accordingly.