[AArch64][SVE][VLS] Move extends into arguments of comparisons

When a comparison is extended and it would be free to extend the
arguments to that comparison, we can propagate the extend into those arguments.
This prevents extra instructions being generated to extend the result of the
comparison, which is not free to extend.

This is a resubmission of D116812 with fixes that need another review.

Differential Revision: https://reviews.llvm.org/D118139