Fixes https://github.com/spring-projects/spring-integration/issues/3501
* make current with latest changes in 'spring-graphql'
* fix checkstyle issues
* implement reactive endpoint for GraphQL Query
* refactor to handle GraphQL Query and Mutation requests
* refactor to handle GraphQL Subscription requests
* implement expressions to handle for various RequestInput parameters
* convert classes to records in tests, remove unneeded datatype modifiers on channels
* replace executionId with idExpression SpEL evaluator
* adjust name and default expression for executionId
* rename for consistency, remove unneeded null check
* Clean up code style
* Remove redundant variables
* Add `What's New` entry
* Add `package-info.java`
f09c665db4