feat: Mouse support

[popey]

What would you like to be added:

The ability to insert mouse location and button presses into the virtual machine.

Why is this needed:

So that tests don't have to rely on a specific number of tab-key presses or up-up-up, down-down-down type navigation in the UI.

Additional context:

Open questions remain about how to keep things tracked on screen within tests. Currently, we're only doing OCR of text. Do we OCR the text of a button, and already know where this is on screen? In the case of the installer, where things move around in frequently, this isn't too much of a problem. But for application testing where buttons could be anywhere, things are a little harder.

A sample test should be supplied that uses the mouse support.

This could be as simple as booting an Ubuntu VM, clicking the top right, and using the shutdown navigation to turn the VM off.