WIP: [wsi] Implement new WSI abstraction

[Joshua-Ashton]

Implements a WSI abstraction and uses it for DXGI. This code has been used in dxvk native for a while, cleaned it up a little bit.

Primarily looking for feedback that this is going in the right direction.

Didn't bother bringing over D3D9 yet, need to rebase and rework some things there.