(aws-apigatewayv2-integrations-alpha): support `TimeoutInMillis` in `WebSocketLambdaIntegration`

### Description

As a [`WebSocketLambdaIntegration`](https://docs.aws.amazon.com/cdk/api/v2/docs/@aws-cdk_aws-apigatewayv2-integrations-alpha.WebSocketLambdaIntegration.html) user
I would like to be able to configure [`TimeoutInMillis`](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-apitgateway-method-integration.html#cfn-apigateway-method-integration-timeoutinmillis)
So that I can customize the timeout.

### Use Case

So that my Web Socket Lambda integration times out sooner than the default 29 seconds.

### Proposed Solution

Add [`timeoutInMillis`](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-apitgateway-method-integration.html#cfn-apigateway-method-integration-timeoutinmillis) as a prop in the [`WebSocketLambdaIntegration`](https://docs.aws.amazon.com/cdk/api/v2/docs/@aws-cdk_aws-apigatewayv2-integrations-alpha.WebSocketLambdaIntegration.html) construct params.

### Other information

Opened on behalf of customer. SIM: V542164665

### Acknowledge

- [ ] I may be able to implement this feature request
- [ ] This feature might incur a breaking change

Start at the WebSocketLambdaIntegration construct and its construct parameters, then trace how integration properties are represented for AWS CloudFormation. Add support for the proposed timeoutInMillis parameter and verify that the synthesized API Gateway integration contains TimeoutInMillis; the issue names no source file or test to run.

Written by the indexing model from the issue text.