[GuardWidening] Add tests showing incorrect behavior of GW.

The first test shows that combineRangeChecks may choose to keep only two poison conditions.
And we cannot do simple arithmetic or logical and in guard.
The second test shows that keeping two poison conditions in the widened guard may allow
execution of side-effect instruction even if just freeze these conditions.
The third test shows that even in simple test we can hoist a poison and even logical and does not help here.

Reviewed By: mkazantsev
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D128779