Use alphanumerical sorting as tie-breaker in case of prefLabel policies result in a tie

[kouralex]

I noticed (due to NatLibFi/Finto-data@26a2d87#diff-b7776f22f1355c1d1fbc86095078db1711cc8e6dea017ad6524fbf3d595617ac) that the preferred value policy selectors are not, by default, deterministic.

I believe these issues could be resolved by appending the policies by a default alphanumerical sorting (there should also be a possibility to reverse this). It should, if possible, be language-dependent as collation order depends on the language of the literal. E.g., 'ä' is sorted before 'b' in English but not in Finnish.

[osma]

There are really two separate aspects here:

1. The preferred value policy selectors are not deterministic. That's bad - they should be.
2. You propose a solution which relies on locale-aware alphanumerical sorting. While that's one possible way to solve the issue, I think there are simpler ways that could be used instead. I'll comment on the PR next...