rename add_reference_lines and reference_bands

[aloctavodia]

This also tweaks the docstrings and examples a little bit.

If you see the example with plot_forest, you will see that the band is incorrectly added to the two columns, not just the forest one. Not sure how to fix this.

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📚 Documentation preview 📚: https://arviz-plots--264.org.readthedocs.build/en/264/

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.04%. Comparing base (28df7c7) to head (fcee553).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #264   +/-   ##
=======================================
  Coverage   73.04%   73.04%           
=======================================
  Files          43       43           
  Lines        5019     5019           
=======================================
  Hits         3666     3666           
  Misses       1353     1353           

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[aloctavodia]

@rohanbabbar04

[OriolAbril]

It is now a bit weird that the generated artists are called ref_line/ref_band but I don't really have a good alternative

[aloctavodia]

Yeah, I also think is weird, but I was not able to think of a better name

[OriolAbril]

Still leaving it open for a bit in case @rohanbabbar04 wants to add something

[rohanbabbar04]

Looks good!!
I think the same question as you guys have already discussed with the names ref_line and ref_band but otherwise it looks fine.