[DA] Fix function `DependenceInfo::isKnownLessThan`

[sjoerdmeijer]

This is extracted from #160924 and little bit of a placeholder (more details will follow), but this is an attempt to document all know DA issues:

The complaint about function DependenceInfo::isKnownLessThan was the following:

At the very least, calling getTruncateOrZeroExtend here is incorrect

I will add this to the meta issue #161805 that lists all DA issues.