Code Review

This pull request introduces a nulls_equal attribute to JoinNode to explicitly handle pandas-style null equality in joins. It includes a new rewrite rule, simplify_join, which optimizes SQL generation by removing unnecessary nullity checks when join columns are non-nullable. The feedback suggests refining the simplify_join logic to be less restrictive by using an and condition for nullability checks, ensuring the optimization is applied more broadly. Additionally, it is recommended to reorder the compiler steps to ensure all join nodes are optimized and to remove an unused import in the new rewrite module.