Introduce spring-boot-autoconfigure-processor

Add an annotation processor that generates properties files for certain
auto-configuration class annotations. Currently attribute values from
@AutoConfigureOrder, @AutoConfigureBefore, @AutoConfigureAfter and
@ConditionalOnClass annotations are stored.

The properties file will allow optimizations to be added in the
`spring-boot-autoconfigure` project. Primarily by removing the need
to ASM parse as many `.class` files.

See gh-7573

spring-boot-devtools/pom.xml

@@ -80,6 +80,11 @@
 			<optional>true</optional>
 		</dependency>
 		<!-- Annotation processing -->
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-autoconfigure-processor</artifactId>
+			<optional>true</optional>
+		</dependency>
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-configuration-processor</artifactId>