Revisit on-demand paging with whv

[0vercl0k]

If I remember correctly, I wasn't able to implement on-demand paging with whv because doing a WHvTranslateGva with an empty environment doesn't generate memory faults like executing would.

This is annoying because wtf does memory translation to be able to set breakpoints where the user wants to; to do that it needs to do a VirtTranslate so I ended up mapping it all at start-up. It's not ideal for obvious reasons but I'm not too sure how to work around that. Just want to revisit this & do the due diligence to make sure that it works as I described and that I didn't miss anything.