fix(logs): ResourcePolicy does not have a defaultChild (#21039)

The L1 construct has the wrong name (should have been `Resource`
but was made to be `ResourcePolicy`).

Explicitly assign the default child.


----
*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk/aws-logs/lib/policy.ts

@@ -46,7 +46,7 @@ export class ResourcePolicy extends Resource {
       physicalName: props?.resourcePolicyName,
     });
 
-    new CfnResourcePolicy(this, 'ResourcePolicy', {
+    const l1 = new CfnResourcePolicy(this, 'ResourcePolicy', {
       policyName: Lazy.string({
         produce: () => props?.resourcePolicyName ?? Names.uniqueId(this),
       }),
@@ -55,6 +55,8 @@ export class ResourcePolicy extends Resource {
       }),
     });
 
+    this.node.defaultChild = l1;
+
     if (props?.policyStatements) {
       this.document.addStatements(...props.policyStatements);
     }

packages/@aws-cdk/aws-logs/test/policy.test.ts

@@ -49,4 +49,15 @@ describe('resource policy', () => {
       PolicyName: 'ResourcePolicy',
     });
   });
+
+  test('ResourcePolicy has a defaultChild', () => {
+    // GIVEN
+    const stack = new Stack();
+
+    // WHEN
+    const resourcePolicy = new ResourcePolicy(stack, 'ResourcePolicy');
+
+    // THEN
+    expect(resourcePolicy.node.defaultChild).toBeDefined();
+  });
 });