Update Actuator to use the new endpoint infrastructure

This commit migrates the Actuator onto the new endpoint infrastruture.
In addition to the existing support for accessing the endpoints via
JMX and HTTP using Spring MVC, support for access via HTTP using
Jersey and WebFlux has been added. This includes using a separate
management port where we now spin up an additional, appropriately
configured servlet or reactive web server to expose the management
context on a different HTTP port to the main application.

Closes gh-2921
Closes gh-5389
Closes gh-9796

spring-boot-samples/spring-boot-sample-actuator/src/test/java/sample/actuator/SampleActuatorApplicationTests.java

@@ -185,7 +185,8 @@ public class SampleActuatorApplicationTests {
 
 	@Test
 	public void traceWithParameterMap() throws Exception {
-		this.restTemplate.getForEntity("/application/health?param1=value1", String.class);
+		this.restTemplate.withBasicAuth("user", getPassword())
+				.getForEntity("/application/health?param1=value1", String.class);
 		@SuppressWarnings("rawtypes")
 		ResponseEntity<List> entity = this.restTemplate
 				.withBasicAuth("user", getPassword())

spring-boot-samples/spring-boot-sample-actuator/src/test/java/sample/actuator/ServletPathInsecureSampleActuatorApplicationTests.java

@@ -62,8 +62,8 @@ public class ServletPathInsecureSampleActuatorApplicationTests {
 	@Test
 	public void testMetricsIsSecure() throws Exception {
 		@SuppressWarnings("rawtypes")
-		ResponseEntity<Map> entity = this.restTemplate.getForEntity("/spring//application/metrics",
-				Map.class);
+		ResponseEntity<Map> entity = this.restTemplate
+				.getForEntity("/spring/application/metrics", Map.class);
 		assertThat(entity.getStatusCode()).isEqualTo(HttpStatus.UNAUTHORIZED);
 	}