Feature request: Add a setup keyword to @testmodule so that it can depend on another @testmodule

[briochemc]

Sometimes one's tests do not rely on all the parts of one's setup. In this case it would be nice to only run the part of the setup that is necessary. This could be done by allowing @testmodule to load other @testmodules.

Example use case: I have a setup that can be split into

1. load data
2. preprocess loaded data
3. do some computation with preprocessed data

and I sometimes want to run tests that only require parts 1 or 2 and avoid the (potentially expensive) part 3. Right now I have a unique @testmodule that does 1, 2, and 3. It would be great to be able to split these into separate @testmodules that depend on each other (1 -> 2 -> 3).