rust_binder: speed up get_node_debug_info using lower_bound iter

Finding the next node in the RBTree can be done more efficiently using
the cursor_lower_bound, as it reduces cost from O(n) to O(log n).

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://github.com/Rust-for-Linux/linux/issues/1249
Suggested-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Rafael Passos <rafael@rcpassos.me>
Link: https://patch.msgid.link/20260814215145.2050599-1-rafael@rcpassos.me
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/android/binder/process.rs

@@ -1216,11 +1216,10 @@ impl Process {
 
         {
             let inner = self.inner.lock();
-            for (node_ptr, node) in &inner.nodes {
-                if *node_ptr > ptr {
-                    node.populate_debug_info(&mut out, &inner);
-                    break;
-                }
+            // cursor_lower_bound retrieves the "key" passed or the next existing larger key
+            if let Some(cursor) = inner.nodes.cursor_lower_bound(&(ptr + 1)) {
+                let (_, node) = cursor.current();
+                node.populate_debug_info(&mut out, &inner);
             }
         }