Change the default behavior to using CBC, as it should always work?

[sebheger]

  Would it be an idea to change the default behavior to using CBC, as it should always work?

Even if Gurobi is not installed (or no license is found) the default code path tries Gurobi first, which takes some time. When done repeatedly (eg in automated tests of tiny models) this can be significant.

Originally posted by @rschwarz in https://github.com/coin-or/python-mip/discussions/313#discussioncomment-4537492