Use findAncestor in more places (#17601)

Author: Andy

src/compiler/utilities.ts

@@ -922,21 +922,11 @@ namespace ts {
     }
 
     export function getContainingFunction(node: Node): FunctionLike {
-        while (true) {
-            node = node.parent;
-            if (!node || isFunctionLike(node)) {
-                return <FunctionLike>node;
-            }
-        }
+        return findAncestor(node.parent, isFunctionLike);
     }
 
     export function getContainingClass(node: Node): ClassLikeDeclaration {
-        while (true) {
-            node = node.parent;
-            if (!node || isClassLike(node)) {
-                return <ClassLikeDeclaration>node;
-            }
-        }
+        return findAncestor(node.parent, isClassLike);
     }
 
     export function getThisContainer(node: Node, includeArrowFunctions: boolean): Node {