fix(ir): avoid deduplicating filters based solely on their name

[cpcloud]

This PR fixes an issue where we were using unwrap_aliases to deduplicate and
enforce expressions by their name in filters.

That approach makes sense in the context of projections, but the name of
predicate expressions in a filter is irrelevant.

The solution was to continue to unwrap aliases but avoid deduplicating
expressions based on their name, and do it solely on the hash value of
expressions.

Closes #9474.

[gforsyth]