Mirroring the MvcConfigurer#addCustomReturnValueHandlers callback which
allows for providing a list of HandlerMethodReturnValueHandler types

Remove 'Method' from RequestMappingHandlerMethodMapping and
RequestMappingHandlerMethodAdapter

Introduce @EnableAsync#order

AsyncAnnotationBeanPostProcessor's 'order' property is now mutable;
@EnableAsync's 'order()' attribute allows for setting it, but must
have a default value, thus uses the new Ordered#NOT_ORDERED
constant - a reserved negative number very unlikely to be otherwise
used that may be interpreted as 'not ordered', useful in annotation
defaulting scenarios where null is not an option.

Introduce first working cut of AsyncConfiguration

Remove AsyncCapability

As a mechanism for setting the 'role' hint on BeanDefinitions created
via component-scanning or @Bean methods.

To provide a reasonable default value for annotations that expose
int-returning #order attributes.

This change is in support of certain polymorphism cases in
@Configuration class inheritance hierarchies.  Consider the following
scenario:

@Configuration
public abstract class AbstractConfig {
    public abstract Object bean();
}

@Configuration
public class ConcreteConfig {
    @Override
    @Bean
    public BeanPostProcessor bean() { ... }
}

ConcreteConfig overrides AbstractConfig's #bean() method with a
covariant return type, in this case returning an object of type
BeanPostProcessor.  It is critically important that the container
is able to detect the return type of ConcreteConfig#bean() in order
to instantiate the BPP at the right point in the lifecycle.

Prior to this change, the container could not do this.
AbstractAutowireCapableBeanFactory#getTypeForFactoryMethod called
ReflectionUtils#getAllDeclaredMethods, which returned Method objects
for both the Object and BeanPostProcessor signatures of the #bean()
method.  This confused the implementation sufficiently as not to
choose a type for the factory method at all.  This means that the
BPP never gets detected as a BPP.

The new method being introduced here, #getUniqueDeclaredMethods, takes
covariant return types into account, and filters out duplicates,
favoring the most specific / narrow return type.

Additionally, it filters out any CGLIB 'rewritten' methods, which
is important in the case of @Configuration classes, which are
enhanced by CGLIB.  See the implementation for further details.

Consolidating internal bean name and aspect class name constats within
AnnotationConfigUtils to allow access from both the context.config
and context.annotation packages without creating a relationship between
the two of them (they are unrelated leaf nodes in the packaging
currently).

The .transaction module does not have a similar utils class and already
has a relationship from transaction.config -> transaction.annotation,
so placing the constants in .annotation.TransactionManagementCapability
to be referenced by .config.AnnotationDrivenBeanDefinitionParser

Allows @Enable* a layer of indirection for deciding which @Configuration
class(es) to @Import.

The @Import annotation may now accept @Configuration class literals
and/or ImportSelector class literals.

@Configuration classes may implement ImportAware in order to be injected
with the AnnotationMetadata of their @Import'ing class.

Includes the introduction of a new PriorityOrdered
ImportAwareBeanPostProcessor that handles injection of the
importing class metadata.

Includes the introduction of AnnotationUtils#findAllAnnotationAttributes
to support iterating through all annotations declared on a given type
and interrogating each for the presence of a meta-annotation. See tests
for details.

@ComponentScan is now checked for explicitly and handled immediately
when parsing @Configuration classes.

Enables @Profile filtering within ComponentScanBeanDefinitionParser

Feature-related support such as @Feature, @FeatureConfiguration,
and FeatureSpecification types will be replaced by framework-provided
@Configuration classes and convenience annotations such as
@ComponentScan (already exists), @EnableAsync, @EnableScheduling,
@EnableTransactionManagement and others.

Issue: SPR-8012,SPR-8034,SPR-8039,SPR-8188,SPR-8206,SPR-8223,
SPR-8225,SPR-8226,SPR-8227

The overloading necessary to preserve the new signature as well as
the old causes ambiguities leading to deprecation warnings in some
caller scenarios.

Issue: SPR-7901

Introduced to support checking return types on @Bean methods but never
actually used.  May be reintroduced as necessary in the future.

Reflecting signature changes in getProperty() methods

- Removed AbstractGenericContextLoader's createGenericApplicationContext() method.
- AnnotationConfigContextLoader now uses an AnnotatedBeanDefinitionReader instead of working with an AnnotationConfigApplicationContext.
- AnnotationConfigContextLoader now uses the supplied GenericApplicationContext to load configuration classes.

Resolve custom args after annotated args, set PATH_WITHIN_HANDLER_MAPPING attribute, and rename resolver for @ExceptionHandler methods

SessionFactory objects created by
SessionFactoryBuilderSupport#buildSessionFactory are now DisposableBean
proxies that call SessionFactory#close and release any threadlocal
DataSource object.

This is the same behavior that has always occurred during LSFBean and
ASFBean destruction lifecycles (and still does). This destruction logic
has now been factored out into
SessionFactoryBuilderSupport#closeHibernateSessionFactory such that all
SFB types can reuse it easily.

Note that LSFBean and ASFBean are subclasses, respectively, of SFBuilder
and ASFBuilder and they each must disable the DisposableBean proxying in
order to avoid duplicate attempts at closing the SessionFactory. See
the implementations of wrapSessionFactoryIfNeccesary() for details.

Issue: SPR-8114

Issue: SPR-8268