fix: wrong hash calculation of plan subtree

- We didn't traverse output during subtree
traversal when calculating hash. Some nodes
(Motion, Projection) store non-trivial
information, which allows to distinguish
different plans. We came across this by
collision between two different queries:
```
SELECT w.n FROM t JOIN w ON t.n = w.n
LIMIT 3

SELECT id, count(*) FROM t
GROUP BY id
HAVING id > 2
LIMIT 3
```
These plan happened to have subtrees that match
exactly except for output of projection, that
we didn't traverse.

- fix this by traversing subtree fully

sbroad-core/src/ir.rs

@@ -1834,7 +1834,7 @@ impl Plan {
     /// # Errors
     /// - serialization error (to binary)
     pub fn pattern_id(&self, top_id: NodeId) -> Result<SmolStr, SbroadError> {
-        let mut dfs = PostOrder::with_capacity(|x| self.subtree_iter(x, false), self.nodes.len());
+        let mut dfs = PostOrder::with_capacity(|x| self.subtree_iter(x, true), self.nodes.len());
         dfs.populate_nodes(top_id);
         let nodes = dfs.take_nodes();
         let mut plan_nodes: Vec<Node> = Vec::with_capacity(nodes.len());