Introduce BeanFactoryAnnotationUtils

Commit 096693c46fba6e09b346a498b7002abd4d6540a9 refactored and
deprecated TransactionAspectUtils, moving its #qualifiedBeanOfType
and related methods into BeanFactoryUtils. This created a package cycle
between beans.factory and beans.factory.annotation due to use of the
beans.factory.annotation.Qualifier annotation in these methods.

This commit breaks the package cycle by introducing
beans.factory.annotation.BeanFactoryAnnotationUtils and moving these
@Qualifier-related methods to it. It is intentionally similar in name
and style to the familiar BeanFactoryUtils class for purposes of
discoverability.

There are no backward-compatibilty concerns associated with this change
as the cycle was introduced, caught and now fixed before a release.

Issue: SPR-6847
Fix package cycle in @EnableSpringConfigured

@EnableSpringConfigured and its @Import'ed
SpringConfiguredConfiguration @Configuration class inadvertently
established a package cycle between beans.factory.aspectj and
context.annotation due to SpringConfiguredConfiguration's
dependency on annotations such as @Configuration, @Bean and @Role.

This commit fixes this architecture bug by moving
@EnableSpringConfigured and SpringConfiguredConfiguration from the
beans.factory.aspectj package to the context.annotation package where
they belong.

This change is assumed to be very low impact as @EnableSpringConfigured
was introduced in 3.1.0 and relocation is happening as quickly as
possible in 3.1.2. @EnableSpringConfigured is assumed to be infrequently
used at this point, and for those that are the migration path
is straightforward. When upgrading from Spring 3.1.0 or 3.1.1, update
import statements in any affected @Configuration classes to reflect the
new packaging.

Issue: SPR-9441
Polish

Issue: SPR-9439
Introduce ConfigurableEnvironment#merge

Prior to this change, AbstractApplicationContext#setParent replaced the
child context's Environment with the parent's Environment if available.
This has the negative effect of potentially changing the type of the
child context's Environment, and in any case causes property sources
added directly against the child environment to be ignored. This
situation could easily occur if a WebApplicationContext child had a
non-web ApplicationContext set as its parent. In this case the parent
Environment type would (likely) be StandardEnvironment, while the child
Environment type would (likely) be StandardServletEnvironment. By
directly inheriting the parent environment, critical property sources
such as ServletContextPropertySource are lost entirely.

This commit introduces the concept of merging an environment through
the new ConfigurableEnvironment#merge method. Instead of replacing the
child's environment with the parent's,
AbstractApplicationContext#setParent now merges property sources as
well as active and default profile names from the parent into the
child. In this way, distinct environment objects are maintained with
specific types and property sources preserved. See #merge Javadoc for
additional details.

Issue: SPR-9444, SPR-9439
Introduce ConfigurableWebEnvironment

Changes introduced in Spring 3.1 for Environment support inadvertently
established a cyclic dependency between the
org.springframework.web.context and
org.springframework.web.context.support packages, specifically through
web.context.ContextLoader's invocation of
web.context.support.WebApplicationContextUtils#initServletPropertySources.

This commit introduces ConfigurableWebEnvironment to break this cyclic
dependency. All web.context.ConfigurableWebApplicationContext types now
return web.context.ConfigurableWebEnvironment from their #getEnvironment
methods; web.context.support.StandardServletEnvironment now implements
ConfigurableWebEnvironment and makes the call to
web.context.support.WebApplicationContextUtils#initServletPropertySources
within its implementation of #initPropertySources. This means that
web.context.ContextLoader now invokes
web.context.ConfigurableWebEnvironment#initPropertySources instead of
web.context.support.WebApplicationContextUtils#initServletPropertySources
and thus the cycle is broken.

Issue: SPR-9439
Merge branch cbeams/SPR-9439

* SPR-9439:
  Introduce ConfigurableWebEnvironment
  Introduce ConfigurableEnvironment#merge
  Polish