[TargetLowering][ARM][AArch64] Remove usage of NoSignedWrap/NoUnsignedWrap...

[TargetLowering][ARM][AArch64] Remove usage of NoSignedWrap/NoUnsignedWrap from AVGFLOOR/CEIL transform.

Use computeOverflowForUnsignedAdd and computeOverflowForSignedAdd
instead. Unfortunately, this recomputes some known bits and sign bits
we may have already computed, but was the easiest fix without a lot
of restructuring.

This recovers the regressions from D151472.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D151858