restore pystring_ascii_new fast path, using PyO3 0.23.3

[davidhewitt]

see PyO3/pyo3#4757

[codspeed-hq]

CodSpeed Performance Report

Merging #180 will not alter performance

_{Comparing dh/pyo3-test (ed8fbbd) with main (06aa3a5)}

Summary

✅ 73 untouched benchmarks

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.75%. Comparing base (06aa3a5) to head (ed8fbbd).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #180   +/-   ##
=======================================
  Coverage   88.75%   88.75%           
=======================================
  Files          13       13           
  Lines        2206     2206           
  Branches     2206     2206           
=======================================
  Hits         1958     1958           
  Misses        153      153           
  Partials       95       95           

Files with missing lines	Coverage Δ
crates/jiter/src/py_string_cache.rs	93.16% <ø> (ø)

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