Q# unit tests: Consider making the simulator specification optional.

[kuzminrobin]

This article makes me think that at least one simulator has to be specified for a unit test (even if the simulator is not used). If we make the simulator specification optional, then we can use the attribute @Test() or @Test("") to specify the unit tests that don't use any simulator. Details.

[bettinaheim]

This would require either an additional language feature (optional arguments, or type parameterized types), or it would require using a different attribute (more reasonable to do that, and this would be a library change only). We can keep the issue tracked here for now.