[libc++][chrono] Implements duration Rep constraints. (#80539)

Applies LWG3050 to the constraints of operator*, operator/, and
operator%. The changes to the constructor were done in
https://reviews.llvm.org/D118902

, but that patch did not identify the
related LWG-issue, and only adjusted the constructor to the wording in
the Standard.

Implements:
- LWG 3050: Conversion specification problem in chrono::duration
constructor

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Co-authored-by: h-vetinari <h.vetinari@gmx.com>