Remove EmuWindow

[CrossVR]

I couldn't find any useful purpose for this class, removing it doesn't seem to break anything.

The most important change to review in this PR is how the window handle is passed around between classes, particularly this instance.

This change has been done in preparation of exclusive fullscreen support, but makes sense on its own hence the PR.

[delroth]

@dolphin-emu-bot rebuild

Might be worth looking who introduced this and asking him why?

[CrossVR]

A git blame just turns up the initial commit, it looks like it's just pure legacy code.

[delroth]

Paging @hrydgard for history lessons :p

[CrossVR]

I forgot to mention in the PR description, this commit removes the code that waits until a window resize is done before resizing the backbuffer. Instead it will now resize the buffers as soon as it's done presenting a frame. In testing this did not result in any issues and it simplifies the code significantly.

However, if it causes any issues I can look into re-implementing that feature.

[hrydgard]

@delroth , lol, you haven't killed this until now? :)