gitadora: (arena model) simulate Realtek device, fix asio redirect hooks (#732)

## Link to GitHub Issue or related Pull Request, if one exists
#730, #718

## Description of change

Part 1)

When ASIO is in use, the game also looks for a Realtek device so that it
can open a WASAPI Exclusive mode stream for headphones.

Add an option to fake that, in case the user doesn't have a Realtek
device.

Part 2)

`-gdaasio` wasn't workign properly - fix the logic.

## Testing
Seems to work with FlexASIO, and Xonar with no real Realtek device.

src/spice2x/hooks/audio/backends/mmdevice/device_collection.cpp

@@ -1,5 +1,6 @@
 #include "device_collection.h"
 #include "device.h"
+#include "null_device.h"
 #include "util/utils.h"
 #include "util/logging.h"
 
@@ -28,17 +29,48 @@ ULONG STDMETHODCALLTYPE WrappedIMMDeviceCollection::Release() {
     return refs;
 }
 
+bool WrappedIMMDeviceCollection::should_inject_fake_realtek() const {
+    return null_render_device_enabled()
+        && (data_flow == eRender || data_flow == eAll);
+}
+
 HRESULT STDMETHODCALLTYPE WrappedIMMDeviceCollection::GetCount(UINT *pcDevices) {
+    // when active, hide all real devices and present only the synthetic one
+    if (should_inject_fake_realtek()) {
+        if (pcDevices == nullptr) {
+            return E_POINTER;
+        }
+        *pcDevices = 1;
+        return S_OK;
+    }
+
     return pReal->GetCount(pcDevices);
 }
 
 HRESULT STDMETHODCALLTYPE WrappedIMMDeviceCollection::Item(UINT nDevice, IMMDevice **ppDevice) {
+    if (ppDevice == nullptr) {
+        return E_POINTER;
+    }
+
+    // when active, the only device in the collection is the synthetic fake Realtek
+    // render device; all real devices are hidden
+    if (should_inject_fake_realtek()) {
+        if (nDevice != 0) {
+            return E_INVALIDARG;
+        }
+        log_info("audio", "WrappedIMMDeviceCollection::Item[{}] -> synthetic fake Realtek render device", nDevice);
+        *ppDevice = new NullMMDevice();
+        return S_OK;
+    }
+
     log_info("audio", "WrappedIMMDeviceCollection::Item[{}]", nDevice);
 
     // call original
     const auto hr = pReal->Item(nDevice, ppDevice);
 
     // wrap interface
-    *ppDevice = new WrappedIMMDevice(*ppDevice);
+    if (SUCCEEDED(hr) && *ppDevice != nullptr) {
+        *ppDevice = new WrappedIMMDevice(*ppDevice);
+    }
     return hr;
 }