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/null_device.h

@@ -0,0 +1,39 @@
+#pragma once
+
+#include <atomic>
+
+#include <mmdeviceapi.h>
+
+// returns true when a synthetic render endpoint should be injected into device
+// enumeration. games like gitadora arena search the render endpoint list for a
+// device whose friendly name contains "Realtek" and crash with a null pointer
+// dereference when no match exists. presenting a fake match that routes to the
+// null audio backend lets the search succeed while discarding the audio.
+bool null_render_device_enabled();
+
+// fake IMMDevice that reports a "Realtek" friendly name and activates straight
+// into the null audio backend, never touching real hardware.
+struct NullMMDevice : IMMDevice {
+    NullMMDevice() = default;
+
+    NullMMDevice(const NullMMDevice &) = delete;
+    NullMMDevice &operator=(const NullMMDevice &) = delete;
+
+    virtual ~NullMMDevice() = default;
+
+#pragma region IUnknown
+    HRESULT STDMETHODCALLTYPE QueryInterface(REFIID riid, void **ppvObj) override;
+    ULONG STDMETHODCALLTYPE AddRef() override;
+    ULONG STDMETHODCALLTYPE Release() override;
+#pragma endregion
+
+#pragma region IMMDevice
+    HRESULT STDMETHODCALLTYPE Activate(REFIID iid, DWORD dwClsCtx, PROPVARIANT *pActivationParams, void **ppInterface) override;
+    HRESULT STDMETHODCALLTYPE OpenPropertyStore(DWORD stgmAccess, IPropertyStore **ppProperties) override;
+    HRESULT STDMETHODCALLTYPE GetId(LPWSTR *ppstrId) override;
+    HRESULT STDMETHODCALLTYPE GetState(DWORD *pdwState) override;
+#pragma endregion
+
+private:
+    std::atomic<ULONG> ref_cnt = 1;
+};