audio: create a wrapper for asio drivers (#731)

## Link to GitHub Issue or related Pull Request, if one exists
n/a

## Description of change
Create `WrappedAsio`, similar to how we wrap `IAudioEndpoint`

So far, the wrapper does these things:

1. logging (for diagnosis, since iidx and gfdm don't produce any logs
when asio succeeds)
2. iidx32+ hack to work around refcount mismatch issue
3. sdvx valk cab hack to force 2-channel audio ("downmixing" by taking
only the front channels)
4. honor volume boost

As a result of `#2` the mempatch was removed from `iidx.cpp` since we
can tackle it cleanly in the hook. `#3` also removes the need for manual
patches.

Real downmixing is hard & expensive on the CPU so it was not
implemented.

## Testing
Tested iidx/sdvx/gfdm with xonar and flexasio

src/spice2x/CMakeLists.txt

@@ -494,6 +494,7 @@ set(SOURCE_FILES ${SOURCE_FILES}
         # hooks
         hooks/audio/acm.cpp
         hooks/audio/audio.cpp
+        hooks/audio/asio_proxy.cpp
         hooks/audio/buffer.cpp
         hooks/audio/mme.cpp
         hooks/audio/util.cpp