PushDownFilterRule does not push down negative literals

Negative literals will show up as a unary operator surrounding a literal. The push down filter rule does not recognize this pattern so it won't push down negative numbers to the storage layer.

The push down filter should recognize negative numbers and translate those literals correctly.

Related to #17062.

Start by locating PushDownFilterRule and read the discussion in related issue #17062. Trace how unary operators around literals are handled during filter pushdown, then verify that negative numbers are translated correctly for the storage layer.

Written by the indexing model from the issue text.