feat(cubesql): Support complex join conditions for grouped joins

* Support COALESCE + IS NOT NULL join condition
* Support IS NOT DISTINCT join condition
* Support expression on top of columns, like CAST

Author: mcheshkov

rust/cubesql/cubesql/src/compile/rewrite/cost.rs

@@ -122,6 +122,9 @@ impl BestCubePlan {
             LogicalPlanLanguage::ProjectionSplitPushDownReplacer(_) => 1,
             LogicalPlanLanguage::ProjectionSplitPullUpReplacer(_) => 1,
             LogicalPlanLanguage::QueryParam(_) => 1,
+            LogicalPlanLanguage::JoinCheckStage(_) => 1,
+            LogicalPlanLanguage::JoinCheckPushDown(_) => 1,
+            LogicalPlanLanguage::JoinCheckPullUp(_) => 1,
             // Not really replacers but those should be deemed as mandatory rewrites and as soon as
             // there's always rewrite rule it's fine to have replacer cost.
             // Needs to be added as alias rewrite always more expensive than original function.

rust/cubesql/cubesql/src/compile/rewrite/mod.rs

@@ -514,6 +514,19 @@ crate::plan_to_language! {
         QueryParam {
             index: usize,
         },
+        JoinCheckStage {
+            expr: Arc<Expr>,
+        },
+        JoinCheckPushDown {
+            expr: Arc<Expr>,
+            left_input: Arc<LogicalPlan>,
+            right_input: Arc<LogicalPlan>,
+        },
+        JoinCheckPullUp {
+            expr: Arc<Expr>,
+            left_input: Arc<LogicalPlan>,
+            right_input: Arc<LogicalPlan>,
+        },
     }
 }
 
@@ -2152,6 +2165,18 @@ fn distinct(input: impl Display) -> String {
     format!("(Distinct {})", input)
 }
 
+fn join_check_stage(expr: impl Display) -> String {
+    format!("(JoinCheckStage {expr})")
+}
+
+fn join_check_push_down(expr: impl Display, left: impl Display, right: impl Display) -> String {
+    format!("(JoinCheckPushDown {expr} {left} {right})")
+}
+
+fn join_check_pull_up(expr: impl Display, left: impl Display, right: impl Display) -> String {
+    format!("(JoinCheckPullUp {expr} {left} {right})")
+}
+
 pub fn original_expr_name(egraph: &CubeEGraph, id: Id) -> Option<String> {
     egraph[id]
         .data