fix(elasticloadbalancingv2): ALB listeners with multiple forwardi… (#…

…25005)

…ng targets need weights specified

The [ELB docs](https://docs.aws.amazon.com/elasticloadbalancing/latest/application/load-balancer-listeners.html#forward-actions) on this aren't explicit, but the examples do _not_ show a configuration with multiple targets, but no weighting. This change assigns a weight to the action, if one wasn't specified.

If specifying stickiness, but no weight, the template will change.

Fixes #24805.

Results in CFN like
  LBListener49E825B4:
    Type: AWS::ElasticLoadBalancingV2::Listener
    Properties:
      DefaultActions:
        - ForwardConfig: TargetGroups: - TargetGroupArn: Ref: TargetGroupOne7810CAFB Weight: 1 - TargetGroupArn: Ref: TargetGroupTwo593946E1 Weight: 1 Type: forward

----

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

packages/@aws-cdk-testing/framework-integ/package.json

@@ -29,20 +29,21 @@
   },
   "license": "Apache-2.0",
   "devDependencies": {
-    "@aws-cdk/cdk-build-tools": "0.0.0",
     "@aws-cdk/aws-batch-alpha": "0.0.0",
-    "delay": "5.0.0",
-    "@aws-cdk/pkglint": "0.0.0"
+    "@aws-cdk/cdk-build-tools": "0.0.0",
+    "@aws-cdk/integ-runner": "^0.0.0",
+    "@aws-cdk/pkglint": "0.0.0",
+    "delay": "5.0.0"
   },
   "dependencies": {
+    "@aws-cdk/integ-tests-alpha": "0.0.0",
     "@aws-cdk/lambda-layer-kubectl-v24": "^2.0.100",
     "aws-cdk-lib": "0.0.0",
     "aws-sdk": "^2.1317.0",
     "aws-sdk-mock": "5.6.0",
     "cdk8s": "^2.7.15",
     "cdk8s-plus-24": "2.4.40",
-    "constructs": "^10.0.0",
-    "@aws-cdk/integ-tests-alpha": "0.0.0"
+    "constructs": "^10.0.0"
   },
   "repository": {
     "url": "https://github.com/aws/aws-cdk.git",

packages/@aws-cdk-testing/framework-integ/test/aws-elasticloadbalancingv2/test/integ.alb.two-target-groups.js.snapshot/Basic.assets.json

@@ -0,0 +1,19 @@
+{
+  "version": "31.0.0",
+  "files": {
+    "5c6a6a70d3025d3d783370635c0a869082ae70a4c11b4e7a0f459cfc4daffb3b": {
+      "source": {
+        "path": "Basic.template.json",
+        "packaging": "file"
+      },
+      "destinations": {
+        "current_account-current_region": {
+          "bucketName": "cdk-hnb659fds-assets-${AWS::AccountId}-${AWS::Region}",
+          "objectKey": "5c6a6a70d3025d3d783370635c0a869082ae70a4c11b4e7a0f459cfc4daffb3b.json",
+          "assumeRoleArn": "arn:${AWS::Partition}:iam::${AWS::AccountId}:role/cdk-hnb659fds-file-publishing-role-${AWS::AccountId}-${AWS::Region}"
+        }
+      }
+    }
+  },
+  "dockerImages": {}
+}