Update dune file using `tests` stanza instead of defining plain executables

The following discussion from !36 (merged) should be addressed:

@raphael-proust started a discussion: (+1 comment)

I think we are due for an update to the dune file using the tests stanza instead of defining executables and alias rules. I think we should do that as a follow-up rather than in this MR. If you agree then just resolve the thread by opening a corresponding issue.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information