add DropdownList

[Wunka]

Depends on #2053
Closes #1920

Currently renders the selected item or the selectable list.

[OneAvargeCoder193]

I would recommend adding an example use case to this pr, maybe where the world gamemode is chosen in the world create menu.

[Wunka]

Example is now fully working. I did not want to work on this due to this weird hover bug.
But this solved itself as it seems. Here is the branch.
I think a lot can be done different based on what its supposed to do.
Currently the dropdownlist only changed between rendering the selected item and the list. But maybe we want the list to be displayed atop of everything else? I would have to look into how I could do that.

[IntegratedQuantum]

I took a look at this today and I think this would be better if it used its own selection and rendering logic.

The current implementation with the selectable list doesn't even look remotely like a dropdown list and I think it would be best if the dropdown would handle its own rendering and selection logic.
Also future logic (e.g. other dropdown often include a hidden search option) is incompatible with a selectable list.

[IntegratedQuantum]

But maybe we want the list to be displayed atop of everything else?

Yes, and with a nice outline and all that.

[Wunka]

I took a look at this today and I think this would be better if it used its own selection and rendering logic.

The current implementation with the selectable list doesn't even look remotely like a dropdown list and I think it would be best if the dropdown would handle its own rendering and selection logic. Also future logic (e.g. other dropdown often include a hidden search option) is incompatible with a selectable list.

Before I start again I will make a few mock ups for the design and will comment them on the dropdown issue.

I will also close this PR for now as I don't know if I will continue with this PR or start from scratch