Enhance sweeps in result shapes tests

[alecandido]

Originally posted by @stavros11 in https://github.com/qiboteam/qibolab/issues/996#issuecomment-2316296324

I would put a docstring in https://github.com/qiboteam/qibolab/blob/6491dcc880eff46ba538beac601df862c4dda875/tests/test_result_shapes.py#L12-L13 saying that return None actually means a 2D sweeper, potentially referring to https://github.com/qiboteam/qibolab/blob/6491dcc880eff46ba538beac601df862c4dda875/tests/conftest.py#L156-L165 where it is defined. As it is now, it gives the impression that we are not testing sweeps at all (that's what I thought for a while).

Correct, it's a bit cryptic. And you can only understand it if you get familiar with the execute fixture.

Also, I think there are a few more cases we could test. Currently, we are only testing a 2D sweep (nested), but we could also introduce some parallel ones, now that they are available (not sure if dummy supports them though?).

Also correct, and definitely possible. But you need somehow to change a bit something deeper about the execute sequence, cf. https://github.com/qiboteam/qibolab/pull/996#issuecomment-2316322837