[ValueTracking] isNonZero sub of ptr2int's with recursive GEP (#68680)

When the sub arguments are ptr2int it is not possible to determine
computeKnownBits() of its arguments.
For scalar case generally sub of 2 ptr2int are converted to sub of
indexes.
However a loop with recursive GEP/PHI where the arguments to sub is of
type ptr2int, if it is possible to determine that a sub of this GEP and
another pointer with the same base is KnownNonZero we can return this.
This helps subsequent passes to optimize the loop further.