feat(lambda): adding .net 8 (dotnet8) lambda runtime support (#29178)

*Co-authored by*: @Beau-Gosse-dev

### Issue # (if applicable)



### Reason for this change

Lambda is launching dotnet8

### Description of changes

new runtime added

### Description of how you validated changes

integ tested

### 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*

packages/@aws-cdk-testing/framework-integ/test/aws-lambda/test/dotnet-handler/handler.cs

@@ -0,0 +1,16 @@
+[assembly: LambdaSerializer(typeof(Amazon.Lambda.Serialization.SystemTextJson.DefaultLambdaJsonSerializer))]
+
+namespace Handler;
+
+public class Function {
+    public Function() {}
+
+    public async Task<APIGatewayProxyResponse> Handler(APIGatewayProxyRequest request) {
+        var id = request.PathParameters["id"];
+
+        return new APIGatewayProxyResponse {
+            StatusCode = (int)HttpStatusCode.OK,
+            Body = JsonSerializer.Serialize(databaseRecord)
+        };
+    }
+}

packages/@aws-cdk-testing/framework-integ/test/aws-lambda/test/integ.runtimes.js.snapshot/aws-cdk-lambda-runtime-management.template.json

@@ -0,0 +1,91 @@
+{
+ "Resources": {
+  "LambdaServiceRoleA8ED4D3B": {
+   "Type": "AWS::IAM::Role",
+   "Properties": {
+    "AssumeRolePolicyDocument": {
+     "Statement": [
+      {
+       "Action": "sts:AssumeRole",
+       "Effect": "Allow",
+       "Principal": {
+        "Service": "lambda.amazonaws.com"
+       }
+      }
+     ],
+     "Version": "2012-10-17"
+    },
+    "ManagedPolicyArns": [
+     {
+      "Fn::Join": [
+       "",
+       [
+        "arn:",
+        {
+         "Ref": "AWS::Partition"
+        },
+        ":iam::aws:policy/service-role/AWSLambdaBasicExecutionRole"
+       ]
+      ]
+     }
+    ]
+   }
+  },
+  "LambdaD247545B": {
+   "Type": "AWS::Lambda::Function",
+   "Properties": {
+    "Code": {
+     "S3Bucket": {
+      "Fn::Sub": "cdk-hnb659fds-assets-${AWS::AccountId}-${AWS::Region}"
+     },
+     "S3Key": "a328343cb12aa16bf2c12bfa98f28509923cf8a0e9771cccbbe967d9e15c08f6.zip"
+    },
+    "Handler": "Handler",
+    "Role": {
+     "Fn::GetAtt": [
+      "LambdaServiceRoleA8ED4D3B",
+      "Arn"
+     ]
+    },
+    "Runtime": "dotnet8"
+   },
+   "DependsOn": [
+    "LambdaServiceRoleA8ED4D3B"
+   ]
+  }
+ },
+ "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."
+    }
+   ]
+  }
+ }
+}