[ty] Avoid overcounting shared memory usage (#19773)

## Summary

Use a global tracker to avoid double counting `Arc` instances.

crates/ruff_memory_usage/src/lib.rs

@@ -0,0 +1,14 @@
+use std::sync::{LazyLock, Mutex};
+
+use get_size2::{GetSize, StandardTracker};
+
+/// Returns the memory usage of the provided object, using a global tracker to avoid
+/// double-counting shared objects.
+pub fn heap_size<T: GetSize>(value: &T) -> usize {
+    static TRACKER: LazyLock<Mutex<StandardTracker>> =
+        LazyLock::new(|| Mutex::new(StandardTracker::new()));
+
+    value
+        .get_heap_size_with_tracker(&mut *TRACKER.lock().unwrap())
+        .0
+}