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

## Summary

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

crates/ty_python_semantic/src/semantic_index/builder.rs

@@ -47,7 +47,7 @@ use crate::semantic_index::symbol::{ScopedSymbolId, Symbol};
 use crate::semantic_index::use_def::{
     EnclosingSnapshotKey, FlowSnapshot, ScopedEnclosingSnapshotId, UseDefMapBuilder,
 };
-use crate::semantic_index::{ArcUseDefMap, ExpressionsScopeMap, SemanticIndex};
+use crate::semantic_index::{ExpressionsScopeMap, SemanticIndex};
 use crate::semantic_model::HasTrackedScope;
 use crate::unpack::{EvaluationMode, Unpack, UnpackKind, UnpackPosition, UnpackValue};
 use crate::{Db, Program};
@@ -1184,7 +1184,7 @@ impl<'db, 'ast> SemanticIndexBuilder<'db, 'ast> {
         let mut use_def_maps: IndexVec<_, _> = self
             .use_def_maps
             .into_iter()
-            .map(|builder| ArcUseDefMap::new(builder.finish()))
+            .map(|builder| Arc::new(builder.finish()))
             .collect();
 
         let mut ast_ids: IndexVec<_, _> = self

crates/ty_python_semantic/src/semantic_index/re_exports.rs

@@ -43,7 +43,7 @@ fn exports_cycle_initial(_db: &dyn Db, _file: File) -> Box<[Name]> {
     Box::default()
 }
 
-#[salsa::tracked(returns(deref), cycle_fn=exports_cycle_recover, cycle_initial=exports_cycle_initial, heap_size=get_size2::heap_size)]
+#[salsa::tracked(returns(deref), cycle_fn=exports_cycle_recover, cycle_initial=exports_cycle_initial, heap_size=ruff_memory_usage::heap_size)]
 pub(super) fn exported_names(db: &dyn Db, file: File) -> Box<[Name]> {
     let module = parsed_module(db, file).load(db);
     let mut finder = ExportFinder::new(db, file);