Implement equals, hashCode, & toString in BeanMethod and *Metadata types

Prior to this commit, ConfigurationClass implemented equals(),
hashCode(), and toString(), but BeanMethod did not.

This commit introduces equals(), hashCode(), and toString()
implementations in BeanMethod for consistency with ConfigurationClass
to make it possible to use BeanMethod instances to index additional
metadata as well.

In order to properly implement equals() in BeanMethod, the method
argument types are required, but these are not directly available in
BeanMethod. However, they are available via ASM when processing @Bean
methods. This commit therefore implements equals(), hashCode(), and
toString() in SimpleMethodMetadata which BeanMethod delegates to.

For completeness, this commit also implements equals(), hashCode(), and
toString() in StandardClassMetadata, StandardMethodMetadata, and
SimpleAnnotationMetadata.

Closes gh-27076

spring-context/src/main/java/org/springframework/context/annotation/BeanMethod.java

@@ -19,6 +19,7 @@ package org.springframework.context.annotation;
 import org.springframework.beans.factory.parsing.Problem;
 import org.springframework.beans.factory.parsing.ProblemReporter;
 import org.springframework.core.type.MethodMetadata;
+import org.springframework.lang.Nullable;
 
 /**
  * Represents a {@link Configuration @Configuration} class method annotated with
@@ -26,6 +27,7 @@ import org.springframework.core.type.MethodMetadata;
  *
  * @author Chris Beams
  * @author Juergen Hoeller
+ * @author Sam Brannen
  * @since 3.0
  * @see ConfigurationClass
  * @see ConfigurationClassParser
@@ -52,6 +54,21 @@ final class BeanMethod extends ConfigurationMethod {
 		}
 	}
 
+	@Override
+	public boolean equals(@Nullable Object obj) {
+		return ((this == obj) || ((obj instanceof BeanMethod) &&
+				this.metadata.equals(((BeanMethod) obj).metadata)));
+	}
+
+	@Override
+	public int hashCode() {
+		return this.metadata.hashCode();
+	}
+
+	@Override
+	public String toString() {
+		return "BeanMethod: " + this.metadata;
+	}
 
 	private class NonOverridableMethodError extends Problem {