* Initialize catch-2 based unit tests
* Add nihstro submodule
Enabled only during testing to help with assembling shaders in-code.
* Implement `ADD` instruction unit-test
* Add arithmetic/logical instruction unit tests
* Add embedded catch2 submodule
Will use the host catch2 if available.
* Add NotImplemented error code
* Add proper handling of SetAppCpuTimeLimit with invalid params
Set default time limit to 0
* Add AppCpuTimeLimit tests
* Replace spaces with tab
