Remove PollControllers from host. Break out a WindowsInputManager from WindowsHost.

Windows/InputDevice.cpp

@@ -20,6 +20,7 @@
 #include <atomic>
 
 #include "Common/Input/InputState.h"
+#include "Common/System/System.h"
 #include "Common/Thread/ThreadUtil.h"
 #include "Core/Config.h"
 #include "Core/Host.h"
@@ -31,7 +32,7 @@ static std::atomic_bool focused = ATOMIC_VAR_INIT(true);
 
 inline static void ExecuteInputPoll() {
 	if (host && (focused.load(std::memory_order_relaxed) || !g_Config.bGamepadOnlyFocused)) {
-		host->PollControllers();
+		System_Notify(SystemNotification::POLL_CONTROLLERS);
 	}
 }