[InstSimplify] regenerate checks using a script

[InstSimplify] regenerate checks using a script

I didn't notice any significant changes in the actual checks here;
all of these tests already used FileCheck, so a script can batch
update them in one shot.

This commit is just to show the value of automating this process:
We have uniform formatting as opposed to a mish-mash of check
structure that changes based on individual prefs and the current
fashion. This makes it simpler to update when we find a bug or
make an enhancement.

llvm-svn: 264457