DSPTool: extract tests into a DSPAssemblyTest

- Moves all test code from DSPTool into UnitTests/Core/DSPAssemblyTest.
- Converts test files (which could only be loaded if they were in the
  shell's working directory, so basically never) into C++ values.
- Enables most of the commented-out tests.
- Removes non-deterministic random code test.

Source/UnitTests/Core/DSP/DSPTestText.h

@@ -0,0 +1,9 @@
+// Copyright 2017 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <string>
+
+extern const char s_dsp_test_text[8434];