refactor(python)!: Set infer_schema_length as keyword-only argument in str.json_decode

[henryharbeck]

Closes #13698

This is a breaking change. If a deprecation is desired first, let me know.

Similar to #7860, the use of this argument is much more natural as a keyword argument, so impact should be limited.
Also stated there, these are hard to properly deprecate due to the Series -> Expr dispatch.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.37%. Comparing base (c81ef69) to head (bbdc1f6).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16835      +/-   ##
==========================================
- Coverage   81.38%   81.37%   -0.01%     
==========================================
  Files        1425     1425              
  Lines      187606   187606              
  Branches     2697     2697              
==========================================
- Hits       152677   152665      -12     
- Misses      34434    34446      +12     
  Partials      495      495              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[stinodego]

This parameter does not technically need to be keyword-only here, but it is everywhere else. So marking them as such here is appropriate, I think.

Deprecation is not required at this point due to low impact.