Add topk information into tree explain plans (#15547)

* Add topk information into tree explain plans

* change display rule for topk label

Author: kumarlokesh

datafusion/physical-plan/src/sorts/sort.rs

@@ -1112,7 +1112,10 @@ impl DisplayAs for SortExec {
 
 impl ExecutionPlan for SortExec {
     fn name(&self) -> &'static str {
-        "SortExec"
+        match self.fetch {
+            Some(_) => "SortExec(TopK)",
+            None => "SortExec",
+        }
     }
 
     fn as_any(&self) -> &dyn Any {

datafusion/sqllogictest/test_files/explain_tree.slt

@@ -889,7 +889,7 @@ explain SELECT * FROM table1 ORDER BY string_col LIMIT 1;
 ----
 physical_plan
 01)┌───────────────────────────┐
-02)│          SortExec         │
+02)│       SortExec(TopK)      │
 03)│    --------------------   │
 04)│          limit: 1         │
 05)│                           │