Closes gh-12529

Refine `BasicErrorController` mappings so that only JSON and XML get
structured responses. A simple string response is returned for all
other media types.

Fixes gh-12513

Fixes gh-12378

Update JAR `Handler` logic so that the existing `jarFile` is only used
if the requested URL starts with the same path. Prior to this commit it
was possible to construct a URL with another URL as context. This could
mean that the `handler` was shared and the already resolved `jarFile`
contained in the handler wasn't necessarily suitable.

Fixes gh-12483

* gh-12511:
  Upgrade maven dependency plugin version to 3.0.2

Closes gh-12511

Previously, the underlying RandomAccessDataFile was not closed when
the JarFile that was using it was closed. This causes a problem on
Windows as the open file handle prevents the file from being deleted.

This commit updates JarFile to close the underlying
RandomAccessDataFile when it is closed and has a JarFileType of
DIRECT.

Previously, when accessing the manifest of a jar file that maps to a
nested directory (BOOT-INF/classes) a new JarFile was created from the
root jar file, the manifest was retrieved, and the new JarFile was
closed. This could lead to the underlying RandomAccessDataFile being
closed while it was still in use.

This commit improves JarFile to retrieve the manifest from the
existing outer JarFile, thereby avoiding the need to create and close
a new JarFile.

Unfortunately, PropertiesLauncher creates a number of scenarios where
a JarFile with a type of direct is closed while it’s still being used.
To accommodate this behaviour, RandomAccessDataFile has been updated
so that it can re-open the underlying RandomAccessFile if it is used
after it has been closed.

Closes gh-12296

This commit disables the default HTML view in the WebFlux error handling
support when `server.error.whitelabel.enabled=false`.
In this case, the original exception will be forwarded down the stream
and handled by the default `WebExceptionHandler` provided by Spring
WebFlux (likely to respond a blank page and an error HTTP response
status).

Closes gh-12520

Closes gh-12516

Closes gh-12515

Update `SpringConfigurationPropertySources` adapter logic so that and
exact instance match is used when checking if the cache can be used.

Prior to this commit if a property source was replaced with one that
had exactly the same name, the adapted version would not change.

Fixes gh-12451

Fixes gh-12478

Fixes gh-12485

Fixes gh-12489

As of Spring Framework 5.0, only Servlet 3.1+ containers are supported.
See https://github.com/spring-projects/spring-framework/wiki/Upgrading-to-Spring-Framework-5.x

This commit updates the reference documentation to reflect that and also
removes sections describing pre-Servlet 3.1 solutions, as those are not
supported anymore.

Fixes gh-12370

Even though War deployment is supported by Spring Framework itself for
WebFlux applications, this is not the case currently in Spring Boot.

Fixes gh-12455

* pr/12495:
  Use ApplicationContextRunner in tests

Closes gh-12495

Closes gh-12503

Closes gh-12502

Closes gh-12501

Closes gh-12500

Closes gh-12499

Closes gh-12393

* pr/12492:
  Fix Javadoc for ServiceLevelAgreementBoundary

Closes gh-12498

Closes gh-12497

Closes gh-12496

Closes gh-12492