Use CDK constructs for websocket API

### Description / Background

When we introduced the REST API, we noticed that the existing use of API Gateway for web socket queries is using the raw CloudFormation CDK constructs instead of the constructs designed for the CDK.

We can adjust this to use the intended constructs as documented in the CDK.

### Technical Notes / Implementation Details

Here's the relevant CDK documentation:

https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_apigatewayv2-readme.html#websocket-api

This needs updating in WebSocketQueryStack.

We've used the proper constructs in RestApiStack.