feat(sns): add delivery policy to sns subscriptions (#30830)

### Issue # (if applicable)

Closes #17576.

### Reason for this change

To allow setting of delivery policy for appropriate sns subscriptions.

### Description of changes



Subscriptions can now take a new parameter `deliveryPolicy` which consists of a `healthyRetryPolicy`, a `throttlePolicy`, and a `requestPolicy` (each having the same parameters described here: https://docs.aws.amazon.com/sns/latest/dg/sns-message-delivery-retries.html#creating-delivery-policy).

### Description of how you validated changes

New integration test along with unit tests.



### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

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

Author: LaurenceWarne

packages/@aws-cdk-testing/framework-integ/test/aws-sns-subscriptions/test/integ.sns-url.js.snapshot/SnsToUrlStack.assets.json

@@ -0,0 +1,64 @@
+{
+ "Resources": {
+  "MyTopic86869434": {
+   "Type": "AWS::SNS::Topic"
+  },
+  "MyTopichttpsfoobarcomDEA92AB5": {
+   "Type": "AWS::SNS::Subscription",
+   "Properties": {
+    "DeliveryPolicy": {
+     "healthyRetryPolicy": {
+      "minDelayTarget": 20,
+      "maxDelayTarget": 21,
+      "numRetries": 10
+     },
+     "throttlePolicy": {
+      "maxReceivesPerSecond": 10
+     },
+     "requestPolicy": {
+      "headerContentType": "application/json"
+     }
+    },
+    "Endpoint": "https://foobar.com/",
+    "Protocol": "https",
+    "TopicArn": {
+     "Ref": "MyTopic86869434"
+    }
+   }
+  }
+ },
+ "Parameters": {
+  "BootstrapVersion": {
+   "Type": "AWS::SSM::Parameter::Value<String>",
+   "Default": "/cdk-bootstrap/hnb659fds/version",
+   "Description": "Version of the CDK Bootstrap resources in this environment, automatically retrieved from SSM Parameter Store. [cdk:skip]"
+  }
+ },
+ "Rules": {
+  "CheckBootstrapVersion": {
+   "Assertions": [
+    {
+     "Assert": {
+      "Fn::Not": [
+       {
+        "Fn::Contains": [
+         [
+          "1",
+          "2",
+          "3",
+          "4",
+          "5"
+         ],
+         {
+          "Ref": "BootstrapVersion"
+         }
+        ]
+       }
+      ]
+     },
+     "AssertDescription": "CDK bootstrap stack version 6 required. Please run 'cdk bootstrap' with a recent version of the CDK CLI."
+    }
+   ]
+  }
+ }
+}