SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.
- 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.