Reimplement compass using DragRotate handler

[jfirebaugh]

Reuse the existing code directly, rather than synthesizing mouse events, which doesn't work on IE (#4784) and triggers mouse event listeners unexpectedly (#5148).

[anandthakker]

👍

A consequence of this is that if you click and hold on the compass button, then moving the mouse will rotate the map as if you'd clicked directly on the map. I think that's fine, just wanted to note it.