feat(apigatewayv2-integrations): WebSocketMockIntegration props (#30622)

### Issue # (if applicable)

None

### Reason for this change

Unlike the other integrations, `WebSocketMockIntegration` did not have a props interface, and was missing a few properties. This PR does not include integration responses, they are already being implemented in #29661 

### Description of changes

* Added `requestTemplates` and `templateSelectionExpression` to the newly created `WebSocketMockIntegrationProps`

### Description of how you validated changes

Unit and integration tests were updated

### 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: nmussy

packages/@aws-cdk-testing/framework-integ/test/aws-apigatewayv2-integrations/test/websocket/integ.mock.js.snapshot/apigatewayv2mockintegrationintegtestDefaultTestDeployAssert3D8FA778.assets.json

@@ -24,8 +24,8 @@
     "ApiId": {
      "Ref": "mywsapi32E6CE11"
     },
-    "RouteKey": "$default",
     "AuthorizationType": "NONE",
+    "RouteKey": "$default",
     "Target": {
      "Fn::Join": [
       "",
@@ -39,14 +39,18 @@
     }
    }
   },
-  "mywsapisendmessageRouteSendMessageIntegrationD29E12F9": {
+  "mywsapisendmessageRouteDefaultIntegration702159AD": {
    "Type": "AWS::ApiGatewayV2::Integration",
    "Properties": {
     "ApiId": {
      "Ref": "mywsapi32E6CE11"
     },
     "IntegrationType": "MOCK",
-    "IntegrationUri": ""
+    "IntegrationUri": "",
+    "RequestTemplates": {
+     "application/json": "{\"statusCode\":200}"
+    },
+    "TemplateSelectionExpression": "\\$default"
    }
   },
   "mywsapisendmessageRouteAE873328": {
@@ -55,29 +59,42 @@
     "ApiId": {
      "Ref": "mywsapi32E6CE11"
     },
-    "RouteKey": "sendmessage",
     "AuthorizationType": "NONE",
+    "RouteKey": "sendmessage",
+    "RouteResponseSelectionExpression": "$default",
     "Target": {
      "Fn::Join": [
       "",
       [
        "integrations/",
        {
-        "Ref": "mywsapisendmessageRouteSendMessageIntegrationD29E12F9"
+        "Ref": "mywsapisendmessageRouteDefaultIntegration702159AD"
        }
       ]
      ]
     }
    }
   },
+  "mywsapisendmessageRouteResponse2ED167D2": {
+   "Type": "AWS::ApiGatewayV2::RouteResponse",
+   "Properties": {
+    "ApiId": {
+     "Ref": "mywsapi32E6CE11"
+    },
+    "RouteId": {
+     "Ref": "mywsapisendmessageRouteAE873328"
+    },
+    "RouteResponseKey": "$default"
+   }
+  },
   "mystage114C35EC": {
    "Type": "AWS::ApiGatewayV2::Stage",
    "Properties": {
     "ApiId": {
      "Ref": "mywsapi32E6CE11"
     },
-    "StageName": "dev",
-    "AutoDeploy": true
+    "AutoDeploy": true,
+    "StageName": "dev"
    }
   }
  },