ref & hist times in bias adjustment methods must match

[coxipi]

Pull Request Checklist:

• This PR addresses an already opened issue (for bug fixes / features)
  • This PR fixes #xyz
• Tests for the changes have been added (for bug fixes / features)
  • (If applicable) Documentation has been added / updated (for bug fixes / features)
• CHANGELOG.rst has been updated (with summary of main changes)
  • Link to issue (:issue:number) and pull request (:pull:number) has been added

What kind of change does this PR introduce?

• Add a method to bias adjustment classes to raise an error if ref and hist times do not match

Does this PR introduce a breaking change?

Other information:

[coxipi]

@aulemahal was this more or less the intent behind _allow_diff_calendars? Or is this just a condition so that map_groups is easier to operate? It seems to be applied pretty broadly, e.g. in Scaling where we would in principle not need such a constraint in this case.

Perhaps I should add a new variable _allow_diff_training_time that would be True for Scaling, but False for the Quantile methods (instead of re-using _allow_diff_calendars?