Add access functions for row duals

[chrhansk]

Could you please add those and ideally release a new version? I need those functions for a project.

[Joao-Dionisio]

Hey, @chrhansk sure! Would you mind adding a quick test, please? Perhaps something in tests/test_lp.py, create a small LP and assert that the result is what you'd expect.

And releasing a new version would be no problem at all, there's a bugfix that we wanted to get out.
But just to make sure, do you know how you can compile your local version of pyscipopt? It would be another possibility for you.

[chrhansk]

I added a small test and updated the Changelog. Problem with the test is that the LP interface does not seem to operate with rows. The test therefore adds a cut and then checks for dual activity after resolving the LP relaxation. The test is unfortunately a bit more fragile, since all other separators have to be deactivated for it to work...

[Joao-Dionisio]

Thank you, @chrhansk! As for the new release, let me just wait on a review for #973, I think it should be done by the end of the week.