Feature: #99093 - Introduce DropDownButton component

See forge#99093


The module menu button bar now can display dropdowns. This enables new interface interactions, like switching the current view from list to tiles or group actions like clipboard and thumbnail visibility. It make the views clearer and the user to see more information at a glance.

Each dropdown consists of different items ranging from headlines to item links that can display the current status. The button automatically changes the icon representation to the icon of the the first active radio icon in the dropdown list.