Add shader-jit unit-tests (#458)

* Rename `dynapica` TU to `shader`

These unit-tests in particular only actually test
the shader-interpreter and not any of the JITs.

* Conditionally test the shader-jit

In the case that the host supports the shader-jit, the interpreter and the shader-jit will both be tested with the same unit-tests. Allowing for even more coverage.

* Remove weird git submodule

CMakeLists.txt

@@ -534,7 +534,7 @@ if(ENABLE_TESTS)
     target_include_directories(nihstro-headers SYSTEM INTERFACE ./third_party/nihstro/include)
 
     add_executable(AlberTests
-        tests/dynapica.cpp
+        tests/shader.cpp
     )
     target_link_libraries(
         AlberTests