AudioCore: Skeleton Implementation

This commit:
* Adds a new subproject, audio_core.
* Defines structures that exist in DSP shared memory.
* Hooks up various other parts of the emulator into audio core.

This sets the foundation for a later HLE DSP implementation.

src/core/hw/gpu.cpp

@@ -17,7 +17,6 @@
 #include "core/core_timing.h"
 
 #include "core/hle/service/gsp_gpu.h"
-#include "core/hle/service/dsp_dsp.h"
 #include "core/hle/service/hid/hid.h"
 
 #include "core/hw/hw.h"
@@ -414,11 +413,6 @@ static void VBlankCallback(u64 userdata, int cycles_late) {
     GSP_GPU::SignalInterrupt(GSP_GPU::InterruptId::PDC0);
     GSP_GPU::SignalInterrupt(GSP_GPU::InterruptId::PDC1);
 
-    // TODO(bunnei): Fake a DSP interrupt on each frame. This does not belong here, but
-    // until we can emulate DSP interrupts, this is probably the only reasonable place to do
-    // this. Certain games expect this to be periodically signaled.
-    DSP_DSP::SignalInterrupt();
-
     // Check for user input updates
     Service::HID::Update();