Temporairly evert "[SCEV] Improve modelling for (null) pointer constants"

This appears to have broken ubsan bot:
https://lab.llvm.org/buildbot/#/builders/85/builds/3062
https://reviews.llvm.org/D98147#2623549

It looks like LSR needs some kind of a change around insertion point handling.
Reverting until i have a fix.

This reverts commit 61f006ac655431bd44b9e089f74c73bec0c1a48c.

GitOrigin-RevId: 329aeb5db43f5e69df038fb20d2def77fe6f8595
5 files changed