Improve performance of `find_max_char`

Feature or enhancement

Proposal:

find_max_char is called each time a string is created.
By reducing the amount of tests, the performance can be improved considerably.

python -m pyperf timeit -s "b=('a' *1000+ '\u019f'*2)" "b[:-1]"

+-----------+--------+----------------------+
| Benchmark | ref    | patch                |
+===========+========+======================+
| timeit    | 442 ns | 388 ns: 1.14x faster |
+-----------+--------+----------------------+

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-122902

Comienza localizando la implementación de find_max_char en CPython y ejecuta el comando pyperf proporcionado con el comportamiento actual. Compara el resultado del benchmark con la referencia indicada de 442 ns y el resultado del parche de 388 ns; se considera terminado cuando el enfoque de pruebas reducido mejora el rendimiento sin cambiar el comportamiento de creación de strings.