touch: make native touch the default for iidx/sdvx/popn (#820)

## Link to GitHub Issue or related Pull Request, if one exists
Fixes #814

## Description of change
Remove iidx/sdvx/popon `native touch` options.

Remove dead code in wintouchemu that deals with these games.

Native touch is now at feature-parity with wintouchemu. Native touch
options work better with touch screens, while rawinput-based wintouchemu
has compat issues on some touchscreens. For these subscreen games
deprecate the usage of wintouchemu and make them use native touch stack
by default.

### For future consideration
Gitadora - not sure what to do with this one. We only use wintouchemu
for the single window case. For all other configurations, the game
accepts mouse and touch input without any hooks, so perhaps nothing
needs to be done here.

Nostalgia - consider moving away from wintouchemu and adopt native touch
hook here as well.

## Testing
WIP

src/spice2x/games/sdvx/sdvx.cpp

@@ -27,7 +27,6 @@
 #include "util/sysutils.h"
 #include "misc/eamuse.h"
 #include "touch/native/nativetouchhook.h"
-#include "misc/wintouchemu.h"
 #include "bi2x_hook.h"
 #include "camera.h"
 #include "io.h"
@@ -49,7 +48,6 @@ namespace games::sdvx {
     const char *ORIGINAL_ASIO_DEVICE_NAME = "XONAR SOUND CARD(64)";
 
     // settings
-    bool NATIVETOUCH = false;
     uint8_t DIGITAL_KNOB_SENS = 16;
     SdvxOverlayPosition OVERLAY_POS = SDVX_OVERLAY_BOTTOM;
     bool ENABLE_COM_PORT_SCAN_HOOK = false;
@@ -455,18 +453,7 @@ namespace games::sdvx {
             }
 
             if (is_valkyrie_model()) {
-                if (NATIVETOUCH) {
-                    nativetouch::hook(avs::game::DLL_INSTANCE);
-                } else if (!NATIVETOUCH && !GRAPHICS_WINDOWED) {
-                    // hook touch window
-                    // in windowed mode, game can accept mouse input on the second screen
-                    wintouchemu::FORCE = true;
-                    wintouchemu::INJECT_MOUSE_AS_WM_TOUCH = true;
-                    wintouchemu::hook_title_ends(
-                            "SOUND VOLTEX",
-                            "Main Screen",
-                            avs::game::DLL_INSTANCE);
-                }
+                nativetouch::hook(avs::game::DLL_INSTANCE);
 
                 // insert BI2X hooks
                 bi2x_hook_init();