Closes gh-5557

Add a @SpyBean annotation that can be used to create spies.

Fixes gh-5538

* pr/5553:
  Polish

Closes gh-5553

* gh-5406:
  Upgrade to Lombok 1.16.8

Closes gh-5406

* version-upgrades:
  Upgrade to Logback 1.1.6

Closes gh-5410

Closes gh-5408

Closes gh-5477

Rework the new testing support so that @SpringApplicationTest can be
used for standard integration tests, web integration tests with a
mock Servlet environment and web integration tests with an embedded
servlet container. This means that it a replacement for 1.3's
@IntegrationTest and @WebIntegrationTest and allows all
SpringApplication testing to be configured using a common annotation.

The old @IntegrationTest and @WebIntegrationTest along with their
supporting classes have been reinstated to their previous form (while
remaining deprecated). This should ensure that they continue to work
in 1.4 exactly as they did in 1.3 giving users a smooth path to
@SpringApplicationTest.

See gh-5477

Fixes gh-5547

It should have been in 68b83a8f but was excluded by gitignore.

See gh-3701

Previously, if loader.path directly specified a jar file that contained
nested archives (.zip or .jar), launching would fail unless those
nested archives were uncompressed. However, if loader.path specified a
directory that contained such a jar file the launch would succeed. This
was because the nested archives within the jar were ignored.

This commit updates PropertiesLauncher so that its behaviour in the
scenarios described above is consistent by not looking for archives
nested with a jar that’s be specified on loader.path. The javadoc for
loader.path has also been updated to make it clear that loader.path
can points to directories or jar files, bringing it into line with
the reference guide.

Closes gh-3701

Following changes to LaunchedURLClassLoader made in 87fe0b2a, it is
no longer necessary for the launcher to load MainMethodRunner via
reflection as both the app class loader that the launcher URL class
loader share the same MainMethodRunner class.

This commit takes advantage of this by updating Launcher to instantiate
MainMethodRunner directly rather than via reflection, removing one
source of possible exceptions in the launcher.

As the MainMethodRunner is now loaded directly and its class is shared
between the two class loaders, there’s no longer a need for it to
implement Runnable. This allows it to throw Exception from its run
method, rather than having to wrap any Exception in a RuntimeException.

Lastly, rather than catching any exception thrown from the launch,
Launcher and its subclasses have been updated to allow this exception
to be thrown from the main method. This allows the Exception to reach
the JVM, to be processed by our registered uncaught exception handler,
and to trigger the JVM’s standard processing for exiting due to a
failure. This removes the need for the Launcher itself to call
System.exit(1) and ensures that the exception is only output to the
console if it hasn’t been registered as a logged exception.

Closes gh-5358

Closes gh-5267

Previously, the documentation included hand-written tables for the
application, production, and technical starters.

This commit replaces the hand-written tables with tables that are
generated automatically from all of the starter poms, thereby ensuring
that the documentation is automatically kept up-to-date as starters
are added and removed. An extra column provided a link to each
starter's pom on GitHub has also been added to the table. This makes
it easier for users to see exactly what each starter contains.

Closes gh-5267

* pr/5532:
  Polish

Closes gh-5532

Closes gh-5309

* pr/5488:
  Upgrade Spring AMQP to 1.6.0.M2

Closes gh-5488

* pr/5521:
  Polish contribution
  Add `defaultValue` property in springProperty tag

Closes gh-5521

This commit adds a `defaultValue` attribute to the `springProperty` tag
of Logback. That attribute can be used to specify a default value.

Closes gh-5447

This commit adds a `spring.jersey.filter.load-on-startup` property used to
customize the startup priority of the Jersey servlet.

Closes gh-5100

This commit updates `Sanitizer` to sanitize by default a key containing
`token`.

Closes gh-5462

* pr/5512:
  Polish contribution
  Add check for non empty list of factories

Closes gh-5512

It was seeen that if a different plugin was used to package Spring Boot
that the project would load but no autoconfiguration actually took
place and many features were mysteriously not working.  Adding a check
to ensure that some factories are always loaded as this is expected.

Closes gh-5465

* pr/5498:
  Polish contribution
  Add useAlwaysMessageFormat configuration key

Closes gh-5498

Allow to configure the `useAlwaysMessageFormat` attribute of
`MessageSource` via configuration.

Closes gh-5483

Previously, the default BuildInfo task created by the DSL was called
buildInfo. Due to Gradle's lack of namespacing for tasks, this meant
there was a slight risk that it could clash with another task. It
also didn't following the naming used by Boot's run task which is
named bootRun.

This commit renames the default BuildInfo task to bootBuildInfo to
match bootRun and to hopefully avoid clashes with tasks from other
plugins.

Closes gh-5518