Refactor actuator package locations

Restructure actuator packages to improve structure. The following
changes have been made:

 - Separate actuator and actuator auto-configuration into different
   modules.
 - Move endpoint code into `spring-boot-actuator`.
 - Move `Endpoint` implementations from a single package into
   technology specific packages.
 - Move `HealthIndicator` implementations from a single package into
   technology specific packages.
 - As much as possible attempt to mirror the `spring-boot` package
   structure and class naming in `spring-boot-actuator` and
   `spring-boot-actuator-autoconfigure`.
 - Move `DataSourceBuilder` and DataSource meta-data support from
   `spring-boot-actuator` to `spring-boot`.

Fixes gh-10261

spring-boot-test/src/main/java/org/springframework/boot/test/context/SpringBootTest.java

@@ -122,10 +122,10 @@ public @interface SpringBootTest {
 		MOCK(false),
 
 		/**
-		 * Creates a (reactive) web application context and sets a {@code server.port=0}
-		 * {@link Environment} property (which usually triggers listening on a random
-		 * port). Often used in conjunction with a {@link LocalServerPort} injected field
-		 * on the test.
+		 * Creates a web application context (reactive or servlet based) and sets a
+		 * {@code server.port=0} {@link Environment} property (which usually triggers
+		 * listening on a random port). Often used in conjunction with a
+		 * {@link LocalServerPort} injected field on the test.
 		 */
 		RANDOM_PORT(true),