Common: Move DebugInterface.h into Core

The base DebugInterface now depends on the Core's CPUThreadGuard, and
utilities in Common shouldn't be depending on Core facilities. So, we
can move this into the core library instead.

Source/Core/Core/PowerPC/PPCSymbolDB.cpp

@@ -19,6 +19,7 @@
 #include "Common/Logging/Log.h"
 #include "Common/StringUtil.h"
 #include "Core/Core.h"
+#include "Core/Debugger/DebugInterface.h"
 #include "Core/PowerPC/MMU.h"
 #include "Core/PowerPC/PPCAnalyst.h"
 #include "Core/PowerPC/PowerPC.h"