fix(cdk/tree): retainining previous objects

fixes component retaining old data in memory even when its not used causing memory usage to increase

fixes #30322

Author: naaajii

src/cdk/tree/tree.ts

@@ -1010,6 +1010,10 @@ export class CdkTree<T, K = T>
       return observableOf([...nodes]);
     }
 
+    // clear previously generated data so we don't keep end up retaining data overtime causing
+    // memory leaks.
+    this._clearPreviousCache();
+
     return observableOf(...nodes).pipe(
       concatMap(node => {
         const parentKey = this._getExpansionKey(node);
@@ -1125,8 +1129,9 @@ export class CdkTree<T, K = T>
       return;
     }
 
-    this._parents.clear();
-    this._ariaSets.clear();
+    // clear previously generated data so we don't keep end up retaining data overtime causing
+    // memory leaks.
+    this._clearPreviousCache();
 
     for (let index = 0; index < flattenedNodes.length; index++) {
       const dataNode = flattenedNodes[index];
@@ -1163,6 +1168,13 @@ export class CdkTree<T, K = T>
       callback(toToggle);
     }
   }
+
+  /** Clears the maps we use to store parents, level & aria-sets in. */
+  private _clearPreviousCache() {
+    this._parents.clear();
+    this._levels.clear();
+    this._ariaSets.clear();
+  }
 }
 
 /**