Split test-binder from core spring-cloud-stream

* Remove all SI test-binder based components from core spring-cloud-stream-module
* Create a new module - spring-cloud-stream-test-binder that contains the test-binder
  and all it's related components
* Migrate tests from core module that use the test-binder into a separate module
  called spring-cloud-stream-integration-tests
* Remove the test-jar dependency using the classifier approach
* Update Spring Cloud Stream BOM with the new test-binder dependency
* Update Schema-Registry tests that use the old approach (using the test-jar with the classifier)
  with the new test-binder dependency

Resolves https://github.com/spring-cloud/spring-cloud-stream/issues/2565

core/spring-cloud-stream-test-binder/pom.xml

@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+		 xmlns="http://maven.apache.org/POM/4.0.0"
+		 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+
+	<artifactId>spring-cloud-stream-test-binder</artifactId>
+	<packaging>jar</packaging>
+	<name>spring-cloud-stream-test-binder</name>
+	<description>Spring Cloud Stream Test Binder</description>
+
+	<parent>
+		<groupId>org.springframework.cloud</groupId>
+		<artifactId>spring-cloud-stream-core</artifactId>
+		<version>4.0.0-SNAPSHOT</version>
+	</parent>
+
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.cloud</groupId>
+			<artifactId>spring-cloud-stream</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-test</artifactId>
+		</dependency>
+	</dependencies>
+
+</project>