PushdownFilter optimizations

 - Add a hidden `Filter::new` constructor that skips type-checking
 - Less allocations, more modification of mutable plan nodes
 - Less cloning, use references when possible

Author: joroKr21

datafusion/expr/src/logical_plan/plan.rs

@@ -2481,6 +2481,15 @@ pub struct Filter {
 }
 
 impl Filter {
+    /// Create a new filter operator.
+    ///
+    /// Skips the type-checking and dealiasing done in [Self::try_new].
+    /// For internal use in DataFusion only.
+    #[doc(hidden)]
+    pub fn new(predicate: Expr, input: Arc<LogicalPlan>) -> Self {
+        Self { predicate, input }
+    }
+
     /// Create a new filter operator.
     ///
     /// Notes: as Aliases have no effect on the output of a filter operator,