Make provider dropdown clickable area the full size of the visible UI element

[jdgarcia]

https://gitkraken.atlassian.net/browse/GKCS-5674

select elements can't have other tags inside them, only text, so at first I though I'd have to create a custom select implementation to handle the "prefix" (PRs: [icon]), or add a dropdown or popover package, but I then thought of a much simpler solution: make the whole thing a select but give it margin left so I can show the custom "prefix" content over it.

Before:

After:

A small side effect is the caret is closer to the edge but that's a result of the caret in native select elements always rendering outside of the select's padding.

[miggy-e]

I'd prefer the caret spacing be slightly padded, but think the full size clickable area is more important