Dropdown component has issues in a similar fancy to #1169. Passing the source es problematic and it's way better to just allow rendering custom items so you can filter them, add separators, etc. Also it doesn't conform very well the spec since the selected option should be placed over the item, etc.

Also, this will come with a Menu reimplementation too. The Dropdown may be consider as an Input with a caret that opens a Menu with a set of selectable options. This will be a good moment to implement #249.