gh-36457: check coprimality of moduli in CRT_basis()
The `xgcd()` calls used in this function to compute modular inverses
already compute the greatest common divisor as a byproduct, so we might
as well add the cheap `.is_one()` check. Benchmarking reveals no
measurable timing difference between the two versions.
URL: https://github.com/sagemath/sage/pull/36457
Reported by: Lorenz Panny
Reviewer(s): Kwankyu Lee
