Improve fpp-to-cpp testing infrastructure

[Kronos3]

Test auto-detection

A lot that goes into test writing is updating boilerplate code and its very easy to make a mistake.

• Add the test to test.sh
• Define it in run.sh
• Add ref updates to update-ref.sh

We can probably add a helper script that will compute the C++ headers/source code that a test would generate and automatically fill in all of these.

Test shadowing

Our tests are grouped by type in directories though each test can still be next to another test. It would be good to generate the .cpp/.hpp in their own directory to more easily determine what was generated by each test. Also if there are overlapping definition in adjacent tests, there won't be ref conflicts.