Implement C++26 `P4037R1`: Supporting `signed char` and `unsigned char` in random number generation

[fbusato]

Is this a duplicate?

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Area

libcu++

Is your feature request related to a problem? Please describe.

Use of signed char or unsigned char in currently results in undefined behavior. Instead, it should be permitted.

Describe the solution you'd like

https://isocpp.org/files/papers/P4037R1.html

Describe alternatives you've considered

No response

Additional context

No response