fix(9870): common expression elimination optimization, should always …

…re-find the correct expression during re-write. (#9871)

* test(9870): reproducer of error with jumping traversal patterns in common-expr-elimination traversals

* refactor: remove the IdArray ordered idx, since the idx ordering does not always stay in sync with the updated TreeNode traversal

* refactor: use the only reproducible key (expr_identifer) for expr_set, while keeping the (stack-popped) symbol used for alias.

* refactor: encapsulate most of the logic within ExprSet, and delineate the expr_identifier from the alias symbol

* test(9870): demonstrate that the sqllogictests are now passing

datafusion/expr/src/logical_plan/plan.rs

@@ -2389,7 +2389,7 @@ impl DistinctOn {
 
 /// Aggregates its input based on a set of grouping and aggregate
 /// expressions (e.g. SUM).
-#[derive(Clone, PartialEq, Eq, Hash)]
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
 // mark non_exhaustive to encourage use of try_new/new()
 #[non_exhaustive]
 pub struct Aggregate {