Summary

I think it would be good to have consistent standards on allowable values for formatting arguments. As far as I can tell, the argument in#15602, which went in in 3.4, is to not add an f-string version for consistency with the library, but starting in 3.3, f-strings became valid direct input into tick formatters

This issue is inspired by#23690 but I didn't want to clobber that discussion with a hashing out of formatting.

Proposed fix

One consistent standard for all the free text formatting functionality - ticks, cursers, and artist labeling like bar/contour/etc. The upside is then I think we can move all the fmt argument parsing to one function/module so messy things like distinguishing % from an fstring happen in one place.

My bias is that most of the formatting arguments should take

1. format (new and old)
2. callable,
3. most of the tick formatters since the tick formatters act on a single tick value at a time and are therefore (mostly? pos seems to always be optional) not really tick specific.

heavily edited to try and make my proposal clearer