This commit ensure that null-safety is consistent between
getters and setters in order to be able to provide beans
with properties with a common type when type safety is
taken in account like with Kotlin.

It also add a few missing property level @Nullable
annotations.

Issue: SPR-15792

This commits extends nullability declarations to the field level, formalizing the interaction between methods and their underlying fields and therefore avoiding any nullability mismatch.

Issue: SPR-15720

Beyond just formally declaring the current behavior, this revision actually enforces non-null behavior in selected signatures now, not tolerating null values anymore when not explicitly documented. It also changes some utility methods with historic null-in/null-out tolerance towards enforced non-null return values, making them a proper citizen in non-null assignments.

Some issues are left as to-do: in particular a thorough revision of spring-test, and a few tests with unclear failures (ignored as "TODO: NULLABLE") to be sorted out in a follow-up commit.

Issue: SPR-15540

This commit introduces 2 new @Nullable and @NonNullApi
annotations that leverage JSR 305 (dormant but available via
Findbugs jsr305 dependency and already used by libraries
like OkHttp) meta-annotations to specify explicitly
null-safety of Spring Framework parameters and return values.

In order to avoid adding too much annotations, the
default is set at package level with @NonNullApi and
@Nullable annotations are added when needed at parameter or
return value level. These annotations are intended to be used
on Spring Framework itself but also by other Spring projects.

@Nullable annotations have been introduced based on Javadoc
and search of patterns like "return null;". It is expected that
nullability of Spring Framework API will be polished with
complementary commits.

In practice, this will make the whole Spring Framework API
null-safe for Kotlin projects (when KT-10942 will be fixed)
since Kotlin will be able to leverage these annotations to
know if a parameter or a return value is nullable or not. But
this is also useful for Java developers as well since IntelliJ
IDEA, for example, also understands these annotations to
generate warnings when unsafe nullable usages are detected.

Issue: SPR-15540

This commit introduces QosSettings that gather the Qualify of Service
settings one can use when sending a message. Such object can now be
associated to any JMS endpoint that allows to send a reply as part of
the processing of an incoming message.

Issue: SPR-15408

Issue: SPR-13440

Issue: SPR-13625

Issue: SPR-13578

Issue: SPR-13774

Issue: SPR-13576

Previously, a custom `DestinationResolver` was not made available
to the underlying `MessageListener`: if a reply needs to be sent, the
default `DestinationResolver` was used.

This commit ensures that if a custom `DestinationResolver` has been set,
it is also configured accordingly for replies.

Issue: SPR-12927

The attributes of @JmsListener allows to specify the reference to a key
in the Environment but @SendTo did not.

This commit fixes this inconsistency so that response destinations are
now also externally configurable.

Issue: SPR-12899

Previously, the "pubSubDomain" drove the resolution of both the
destination of the listener and the default response destination.

A new "replyPubSubDomain" attribute has been added on the base listener
and  can be used to listen on a topic and reply to a queue (or vice
versa). The attribute is exposed via the "response-destination-type" XML
attribute on the listener container element. It is also available on the
JmsListenerContainerFactory for use with the @JmsListener infrastructure.

Issue: SPR-12911

Previously, the default reply destination could not be discovered if the
@JmsListener annotation was placed on a bean that is eligible for
proxying as the proxy method is used internally and does not reveal
an annotation placed on the implementation.

This commit makes sure to resolve the most specific method when
searching that annotation.

Issue: SPR-12513

This commit moves JmsHandlerMethodFactory and its default
implementation to the messaging abstraction. Working on a similar
support for AMQP revealed that this factory has nothing that is JMS
specific and is exactly identical in the case of AMQP.

Issue: SPR-12053

Issue: SPR-9882
Issue: SPR-11969

This commit removes the queue attribute of the JmsListener annotation
as this information should be provided by the container factory and not
by each individual listener endpoints.

There was a side effect that an annotation value cannot be null, which
was forcing the container to be a queue-based container by default.

Issue: SPR-9882

This commit replaces the "responseDestination" attribute on the
JmsListener annotation by a support of the standard SendTo annotation.

Issue: SPR-11707

This commit adds the support of JMS annotated endpoint. Can be
activated both by @EnableJms or <jms:annotation-driven/> and
detects methods of managed beans annotated with @JmsListener,
either directly or through a meta-annotation.

Containers are created and managed under the cover by a registry
at application startup time. Container creation is delegated to a
JmsListenerContainerFactory that is identified by the containerFactory
attribute of the JmsListener annotation. Containers can be
retrieved from the registry using a custom id that can be specified
directly on the annotation.

A "factory-id" attribute is available on the container element of
the XML namespace. When it is present, the configuration defined at
the namespace level is used to build a JmsListenerContainerFactory
that is exposed with the value of the "factory-id" attribute. This can
be used as a smooth migration path for users having listener containers
defined at the namespace level. It is also possible to migrate all
listeners to annotated endpoints and yet keep the
<jms:listener-container> or <jms:jca-listener-container> element to
share the container configuration.

The configuration can be fine-tuned by implementing the
JmsListenerConfigurer interface which gives access to the registrar
used to register endpoints. This includes a programmatic registration
of endpoints in complement to the declarative approach. A default
JmsListenerContainerFactory can also be specified to be used if no
containerFactory has been set on the annotation.

Annotated methods can have flexible method arguments that are similar
to what @MessageMapping provides. In particular, jms listener endpoint
methods can fully use the messaging abstraction, including convenient
header accessors. It is also possible to inject the raw
javax.jms.Message and the Session for more advanced use cases. The
payload can be injected as long as the conversion service is able to
convert it from the original type of the JMS payload. By
default, a DefaultJmsHandlerMethodFactory is used but it can be
configured further to support additional method arguments or to
customize conversion and validation support.

The return type of an annotated method can also be an instance of
Spring's Message abstraction. Instead of just converting the payload,
such response type allows to communicate standard and custom headers.

The JmsHeaderMapper infrastructure from Spring integration has also
been migrated to the Spring framework. SimpleJmsHeaderMapper is based
on SI's DefaultJmsHeaderMapper. The simple implementation maps all
JMS headers so that the generated Message abstraction has all the
information stored in the protocol specific message.

Issue: SPR-9882