gh-37157: Add additional lattice methods for matrices over QQ
LLL has long been implemented for matrices over QQ by clearing the
denominator and doing LLL over ZZ, but this was not done for BKZ() or
is_LLL_reduced()
This PR adds BKZ() and is_LLL_reduced() to rational matrices, using the
same techniques as the current LLL method.
URL: https://github.com/sagemath/sage/pull/37157
Reported by: TheBlupper
Reviewer(s): grhkm21