[fix](Nereids) top-n with top project should hit top-n opt (#29971)

in PR #29312, we limit top-n opt only enable in simplest cases.
in this PR, we let go of some restrictions.

fe/fe-core/src/main/java/org/apache/doris/nereids/processor/post/TopNScanOpt.java

@@ -52,6 +52,14 @@ public Plan visit(Plan plan, CascadesContext context) {
     public Plan visitPhysicalSink(PhysicalSink<? extends Plan> physicalSink, CascadesContext context) {
         if (physicalSink.child() instanceof TopN) {
             return super.visit(physicalSink, context);
+        } else if (physicalSink.child() instanceof Project && physicalSink.child().child(0) instanceof TopN) {
+            PhysicalTopN<?> oldTopN = (PhysicalTopN<?>) physicalSink.child().child(0);
+            PhysicalTopN<?> newTopN = (PhysicalTopN<?>) oldTopN.accept(this, context);
+            if (newTopN == oldTopN) {
+                return physicalSink;
+            } else {
+                return physicalSink.withChildren(physicalSink.child().withChildren(newTopN));
+            }
         }
         return physicalSink;
     }