Reduce log level to DEBUG when @TELs isn't present

The default set of TestExecutionListeners is sufficient in most
integration testing scenarios; however, the TestContextManager
nonetheless logs an INFO message if the @TestExecutionListeners
annotation is not present on an integration test class.

In order to avoid flooding the logs with messages about the absence of
@TestExecutionListeners, this commit reduces the log level for such
messages from INFO to DEBUG.

Issue: SPR-8645
RTU.setField() shouldn't call toString() on target

ReflectionTestUtils.setField() implicitly calls toString() on the target
object when arguments for a call to Assert.notNull() are built. This can
have undesirable side effects, for example if the toString() invocation
results in a thrown exception or access to an external system (e.g., a
database).

This commit addresses this issue by inlining the Assert.notNull() code,
thereby avoiding accidental invocation of toString() on a non-null
target.

Issue: SPR-9571
Expand repackaged asm/cglib jars into spring-core

Prior to this change, the repackaged spring-asm and spring-cglib jars
were being included wholesale in the spring-core jar, whereas the
intention was to include the unzipped classfiles.

This change ensures that spring-asm and spring-cglib jars are unzipped
on the fly when creating the spring-core jar.

Issue: SPR-9669
XStreamMarshaller supports stream directly

XStreamMarshaller now supports writing to OutputStreams and reading from
InputStreams directly, as opposed to wrapping streams in a
OutputStreamWriter or InputStreamReader.

Issue: SPR-9663
Make spring-orm dependency on spring-web optional

Historically spring-orm has had an optional dependency on spring-web,
primarily in support of OpenSessionInView functionality. This optional
dependency was inadvertently made required when porting the build to
Gradle. This commit simply reintroduces the optional setting.

Issue: SPR-9632
Add optional AspectJ dependencies where appropriate

spring-core, spring-aop and spring-context each have compile-time
dependencies on classes in the aspectjweaver jar. Prior to this commit,
only spring-core declared an optional dependency on it; now all three
do.

Issue: SPR-9683
Polish Spring MVC ContextLoader

This commit polishes the exception message thrown by customizeContext()
for greater readability.
Introduced ControllerAdvice annotation

Classes with this annotation can contain @ExceptionHandler,
@InitBinder, and @ModelAttribute methods that apply to all controllers.
The new annotation is also a component annotation allowing
implementations to be discovered through component scanning.

Issue: SPR-9112
Implement invalidate() properly in MockHttpSession

The invalidate() method in MockHttpSession is currently implemented
incorrectly. According to the Servlet specification, the method should
throw an IllegalStateException if it is invoked on an already
invalidated session. However, invoking invalidate() on the same
MockHttpSession instance multiple times does not throw an exception.

This commits addresses this issue by checking the invalid field and
throwing an IllegalStateException if it has already been set to true.

Issue: SPR-9686
Update MockHttpSession across the test suite
Make DeferredResult more usable and testable

DeferredResult now has a setErrorResult method that can be set to an
Exception or an error object, error view, etc.

The new isSetOrExpired() method can be used to check pro-actively if
the DeferredResult is still usable or not.

The setDeferredResultHandler method is now public so tests may use it.

Issue: SPR-9690, SPR-9689
Set timeout value and task executor per async request

Methods returning DeferredResult can now specify a timeout value
through constructor arg while methods returning a Callable can wrap it
in an AsyncTask that also accepts a timeout and a specific task
executor.

Issue: SPR-9399
Update remaining filter with async support

Issue: SPR-9433
Add async options to MVC namespace and Java config

The MVC Java config method to implement is
WebMvcConfigurer.configureAsyncSupport(AsyncSupportConfigurer)

The MVC namespace element is:
<mvc:annotation-driven>
  <mvc:async-support default-timeout="2500" task-executor="myExecutor" />
</mvc:annotation-driven>

Issue: SPR-9694
Support ApplicationContextInitializers in the TCF

Starting with Spring 3.1 applications can specify
contextInitializerClasses via context-param and init-param in web.xml;
however, there is currently no way to have such initializers invoked in
integration testing scenarios without writing a custom
SmartContextLoader. For comprehensive integration testing it should
therefore be possible to re-use ApplicationContextInitializers in the
Spring TestContext Framework as well.

This commit makes this possible at the @ContextConfiguration level by
allowing an array of ACI types to be specified, and the out-of-the-box
SmartContextLoader implementations invoke the declared initializers at
the appropriate time.

 - Added initializers and inheritInitializers attributes to
   @ContextConfiguration.

 - Introduced support for ApplicationContextInitializers in
   ContextConfigurationAttributes, MergedContextConfiguration, and
   ContextLoaderUtils.

 - MergedContextConfiguration stores context initializer classes as a
   Set and incorporates them into the implementations of hashCode() and
   equals() for proper context caching.

 - ApplicationContextInitializers are invoked in the new
   prepareContext(GenericApplicationContext, MergedContextConfiguration)
   method in AbstractGenericContextLoader, and ordering declared via the
   Ordered interface and @Order annotation is honored.

 - Updated DelegatingSmartContextLoader to support initializers.
   Specifically, a test class may optionally declare neither XML
   configuration files nor annotated classes and instead declare only
   application context initializers. In such cases, an attempt will
   still be made to detect defaults, but their absence will not result
   an an exception.

 - Documented support for application context initializers in Javadoc
   and in the testing chapter of the reference manual.

Issue: SPR-9011
Merge pull request #121 from sbrannen/SPR-9011

* SPR-9011:
  Support ApplicationContextInitializers in the TCF
Add ExceptionHandlerSupport class

The new class is functionally equivalent to the
DefaultHandlerExceptionResolver (i.e. it translates Spring MVC
exceptions to various status codes) but uses an @ExceptionHandler
returning a ResponseEntity<Object>, which means it can be customized to
write error content to the body of the response.

Issue: SPR-9290
Add error message for missing servlet request param.

The DefaultHandlerExceptionResolver now provides an error message in
addition to setting the status of the response.

Issue: SPR-9312
Allow Errors after @RequestBody and @RequestPart

An @RequestBody or an @RequestPart argument can now be followed by an
Errors/BindingResult argument making it possible to handle validation
errors (as a result of an @Valid annotation) locally within the
@RequestMapping method.

Issue: SPR-7114
Decode target parameters prior to saving a FlashMap

The target parameters for a FlashMap must be decoded to be able to
match them to the parameters of incoming requests given that the
HttpServletRequest returns decoded request parameters.

SPR-9657