ImGui is now initialized once at startup and shutdown before
terminating. graphics initialization is independent.
Move more imgui stuff into imgui drivers.
switch: set scaling on external screen to 1.4, same as xbox
UI scaling refactoring.
single-threaded mode similar to libretro core
stateful Emulator object
disable memory watcher when !gppo
ggpo: poll input as late as possible in !threaded
Flyinghead