Don't subclass str

[DanielNoord]

Taken from #2586

Let's not subclass str as that breaks mypyc and is a bad pattern anyway.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.30%. Comparing base (68356ea) to head (8cd4629).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2594      +/-   ##
==========================================
- Coverage   99.39%   99.30%   -0.10%     
==========================================
  Files          41       41              
  Lines        3147     3149       +2     
  Branches      680      680              
==========================================
- Hits         3128     3127       -1     
- Misses         11       14       +3     
  Partials        8        8              

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