GR backend: use textext for :log2 and :ln axis scaling

[pjaap]

This fixes #4871

Only the case of :log10 has been treated before.

Description

Attribution

• [ x] I am listed in .zenodo.json (see How to get acknowledged #3503)

Things to consider

• Does it work on log scales?
• Does it work in layouts?
• Does it work in recipes?
• Does it work with multiple series in one call?
• PR includes or updates tests?
• PR includes or updates documentation?

[pjaap]

Should this go into master an/or v2 branch?
The same fix can be applied to https://github.com/JuliaPlots/Plots.jl/blob/v2/PlotsBase/ext/GRExt.jl#L434 and https://github.com/JuliaPlots/Plots.jl/blob/v2/PlotsBase/ext/GRExt.jl#L443

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.14%. Comparing base (fa65e7d) to head (a08a88c).
Report is 26 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4991      +/-   ##
==========================================
- Coverage   89.77%   87.14%   -2.63%     
==========================================
  Files          40       41       +1     
  Lines        8780     9081     +301     
==========================================
+ Hits         7882     7914      +32     
- Misses        898     1167     +269     

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[BeastyBlacksmith]

Should this go into master an/or v2 branch?

Ideally both

[pjaap]

Ok, sure. Then I'll open another PR for v2 once this is merged. What needs to be done to get this here merged?

[pjaap]

Thanks for merging. The other one is #4993

[BeastyBlacksmith]

Thanks for contributing!