Solver.lookup ignores solver versions

[informarte]

The --solver option of minizinc supports solver versions (e.g. --solver my-solver@1.0) by considering the version information provided by the solver definitions. Solver.lookup, however, ignores version information, i.e. it chooses a random version if several versions are installed. This lack of functionality makes it hard to compare different versions of a solver. The only way is to deinstall or disable (by removing solver definition files) all versions except for one, test it, then change the setup, and so on. It's a tedious and error-prone process.

[Dekker1]

It appears that the version addition is currently never added to the list of tags it uses to find the solver. However, I'm very surprised that the information would just be ignored. Looking at the code, I would expect that Solver.lookup("my-solver@1.0") would always result in an exception: https://github.com/MiniZinc/minizinc-python/blob/develop/src/minizinc/solver.py#L139-L143

I think there are two things to be done here:

1. To add tags that include the version: split at major, split at minor, or full version. This would allow the lookup for version annotated identifiers, e.g. my-solver@1.0.0, my-solver@1.0, and my-solver@1.
2. To ensure that the tag maps for identifiers remain in sorted order. This would ensure that if multiple version of my-solver are present, then the newest version can be chosen.