PR Summary

Force the update ofall the tick labels, even the ones that are not drawn. This addresses the issue#9397 where incorrect labels are returned when some ticks are outside of the displayed range. Please note that the fix idea is@anntzer's one.

PR Checklist

• Has Pytest style unit tests
• [?] Code is PEP 8 compliant=> Well let's CI confirm ^^
• New features are documented, with examples if plot related
• Documentation is sphinx and numpydoc compliant
• Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
• [?] Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way=>@tacaswell Should I add an entry?

Milestoning it for 2.1.1 as it looks like a minor bugfix to me but feel free to postpone it to 2.2 if somebody thinks that it would be better. (see edit)

Supplementary question: should I rebase against the 2.1.x branch?

Edit: re-milestoning it for v2.2, accordingly to what@dstansby suggested in#9397.