Improve ergonomics of 'test-suite'

[TomMD]

The test suite has a field of type. The vast majority of the type the type is exitcode-stdio-1.0. I propose that we make that type the default and allow the field to be omitted.

[Mikolaj]

That's a great idea. The proof: something like that has already been proposed. Does this cover your proposal: #7459?

[TomMD]

Gah, closing!