fix(elasticache): security group for ServerlessCache does not use default endpoint port (#35738)

### Issue # (if applicable)

N/A

### Reason for this change



A security group ingress for the new `ServerlessCache` construct does not use an endpoint port.

The following CDK code generates an INVALID CFn template with `null` for `FromPort` and `ToPort`:

```ts
    const cache = new ServerlessCache(this, 'ServerlessCache', {
      vpc,
    });
    const sg = new SecurityGroup(this, 'SecurityGroup', {
      vpc,
    });
    sg.connections.allowToDefaultPort(cache);
```

```json
  "SecurityGroupfromawscdkserverlesscacheClientSG6D18D5F9IndirectPortFE633A67": {
   "Type": "AWS::EC2::SecurityGroupIngress",
   "Properties": {
    // ...
    // ...
    "FromPort": null,
    // ...
    // ...
    "ToPort": null
   },
```

An expected template:

```json
  "SecurityGroupfromawscdkserverlesscacheClientSG6D18D5F9IndirectPortFE633A67": {
   "Type": "AWS::EC2::SecurityGroupIngress",
   "Properties": {
    // ...
    // ...
    "FromPort": {
     "Fn::GetAtt": [
      "Cache18F6EE16",
      "Endpoint.Port"
     ]
    },
    // ...
    // ...
    "ToPort": {
     "Fn::GetAtt": [
      "Cache18F6EE16",
      "Endpoint.Port"
     ]
    }
   }
  },
```

FYI: The method `cache.connections.defaultPort?.toRuleJson()` outputs `{"Value":{"ipProtocol":"tcp","fromPort":null,"toPort":null}}`. But we expect `{"Value":{"ipProtocol":"tcp","fromPort":{"Fn::GetAtt":["Cache18F6EE16","Endpoint.Port"]},"toPort":{"Fn::GetAtt":["Cache18F6EE16","Endpoint.Port"]}}}`.

### Description of changes



Use `Token.asNumber` for the `defaultPort` of `Connections` in `ServerlessCache`:

```diff
    this.connections = new ec2.Connections({
      securityGroups: this.securityGroups,
-      defaultPort: ec2.Port.tcp(Lazy.number({ produce: () => parseInt(this.serverlessCacheEndpointPort) })),
+      defaultPort: ec2.Port.tcp(Token.asNumber(this.serverlessCacheEndpointPort)),
    });
```

### Describe any new or updated permissions being added




### Description of how you validated changes



Both an unit test and an integ test.

### 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: go-to-k

packages/@aws-cdk/aws-elasticache-alpha/lib/serverless-cache.ts

@@ -469,7 +469,7 @@ export class ServerlessCache extends ServerlessCacheBase {
 
     this.connections = new ec2.Connections({
       securityGroups: this.securityGroups,
-      defaultPort: ec2.Port.tcp(Lazy.number({ produce: () => parseInt(this.serverlessCacheEndpointPort) })),
+      defaultPort: ec2.Port.tcp(Token.asNumber(this.serverlessCacheEndpointPort)),
     });
 
     Object.defineProperty(this, ELASTICACHE_SERVERLESSCACHE_SYMBOL, { value: true });

…6dedf53475c933aed3069238.bundle/index.js …c8b1bb373e93297e26aec564.bundle/index.jspackages/@aws-cdk/aws-elasticache-alpha/test/integ.serverless-cache.js.snapshot/asset.53e3ecec991005bc2ddc98d13a897e8eadf082b86dedf53475c933aed3069238.bundle/index.js renamed to packages/@aws-cdk/aws-elasticache-alpha/test/integ.serverless-cache.js.snapshot/asset.c11608a15785084ea1afe65826e575ee316add10c8b1bb373e93297e26aec564.bundle/index.js packages/@aws-cdk/aws-elasticache-alpha/test/integ.serverless-cache.js.snapshot/asset.53e3ecec991005bc2ddc98d13a897e8eadf082b86dedf53475c933aed3069238.bundle/index.js renamed to packages/@aws-cdk/aws-elasticache-alpha/test/integ.serverless-cache.js.snapshot/asset.c11608a15785084ea1afe65826e575ee316add10c8b1bb373e93297e26aec564.bundle/index.js

@@ -546,6 +546,37 @@
     }
    }
   },
+  "SecurityGroupfromawscdkserverlesscacheClientSG6D18D5F9IndirectPortFE633A67": {
+   "Type": "AWS::EC2::SecurityGroupIngress",
+   "Properties": {
+    "Description": "from awscdkserverlesscacheClientSG6D18D5F9:{IndirectPort}",
+    "FromPort": {
+     "Fn::GetAtt": [
+      "Cache18F6EE16",
+      "Endpoint.Port"
+     ]
+    },
+    "GroupId": {
+     "Fn::GetAtt": [
+      "SecurityGroupDD263621",
+      "GroupId"
+     ]
+    },
+    "IpProtocol": "tcp",
+    "SourceSecurityGroupId": {
+     "Fn::GetAtt": [
+      "ClientSG4CAE4F40",
+      "GroupId"
+     ]
+    },
+    "ToPort": {
+     "Fn::GetAtt": [
+      "Cache18F6EE16",
+      "Endpoint.Port"
+     ]
+    }
+   }
+  },
   "User00B015A1": {
    "Type": "AWS::ElastiCache::User",
    "Properties": {
@@ -622,6 +653,22 @@
    ],
    "UpdateReplacePolicy": "Delete",
    "DeletionPolicy": "Delete"
+  },
+  "ClientSG4CAE4F40": {
+   "Type": "AWS::EC2::SecurityGroup",
+   "Properties": {
+    "GroupDescription": "aws-cdk-serverless-cache/ClientSG",
+    "SecurityGroupEgress": [
+     {
+      "CidrIp": "0.0.0.0/0",
+      "Description": "Allow all outbound traffic by default",
+      "IpProtocol": "-1"
+     }
+    ],
+    "VpcId": {
+     "Ref": "VPCB9E5F0B4"
+    }
+   }
   }
  },
  "Parameters": {