GH-3501: Add GraphQL support

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`

spring-integration-graphql/src/test/resources/graphql/test-schema.graphqls

@@ -0,0 +1,20 @@
+type Query {
+    testQuery: QueryResult
+    testQueryById(id: String): QueryResult
+}
+
+type Mutation {
+    update(id: String!): Update!
+}
+
+type Subscription {
+    results: QueryResult
+}
+
+type QueryResult {
+    id: String
+}
+
+type Update {
+    id: String
+}

spring-integration-graphql/src/test/resources/log4j2-test.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Configuration status="WARN">
+	<Appenders>
+		<Console name="STDOUT" target="SYSTEM_OUT">
+			<PatternLayout pattern="%d %p [%t] [%c] - %m%n" />
+		</Console>
+	</Appenders>
+	<Loggers>
+		<Logger name="org.springframework" level="warn"/>
+		<Logger name="org.springframework.graphql" level="warn"/>
+		<Logger name="org.springframework.integration.graphql" level="warn"/>
+		<Root level="warn">
+			<AppenderRef ref="STDOUT" />
+		</Root>
+	</Loggers>
+</Configuration>