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

## Summary

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

crates/ty_python_semantic/src/util/get_size.rs

@@ -1,15 +0,0 @@
-use std::sync::Arc;
-
-use get_size2::GetSize;
-
-/// By default, `Arc<T>: GetSize` requires `T: 'static` to enable tracking references
-/// of the `Arc` and avoid double-counting. This method opts out of that behavior and
-/// removes the `'static` requirement.
-///
-/// This method will just return the heap-size of the inner `T`.
-pub(crate) fn untracked_arc_size<T>(arc: &Arc<T>) -> usize
-where
-    T: GetSize,
-{
-    T::get_heap_size(&**arc)
-}

crates/ty_python_semantic/src/util/mod.rs

@@ -1,3 +1,2 @@
 pub(crate) mod diagnostics;
-pub(crate) mod get_size;
 pub(crate) mod subscript;