Rework the test suite such as we have larger tests with meaningful names

[deadalnix]

Right now we have a bunch of testNNNN.d , but that is not really practical, especially since their number have grown significantly.

A better way to do things would have topical files that check that area of the language have proper semantic.

[maxhaton]

Folders would also be good e.g. small focused feature tests and large-er reductions shouldn't be dumped in the same folder