Closes gh-10923

* pr/11630:
  Polish

Closes gh-11630

This commit updates DefaultErrorAttributes to handle
ResponseStatusException explicitly. This exception is used in a
WebFlux application to signal that the processing of the query has
failed with an HTTP status code and a reason phrase. The latter is now
properly mapped to the `message` attribute of the response body.

Closes gh-11614

* pr/11619:
  Upgrade to Spring Session 2.0.0.RELEASE

Closes gh-11619

* pr/11622:
  Remove an unnecessary assertion

Closes gh-11622

Closes gh-10976

See gh-11598

* pr/11606:
  Fix typo in DynamicRegistrationBean class name

Closes gh-11606

* pr/11598:
  Polish "Upgrade to Micrometer 1.0.0-rc.6"
  Upgrade to Micrometer 1.0.0-rc.6

Closes gh-11598

See gh-11598

Fixes gh-11318

Closes gh-11602

This commit partially reverts the changes made in ec470fbe. While
the started message continues to be logged before any application and
command line runners are called, the publishing of
ApplicationReadyEvent now happens after the runners have been called.
Additionally, a new event, named ApplicationStartedEvent, has been
introduced. This new event is published after the context has been
refreshed but before any application and command line runners are
called.

Closes gh-11484

The reworking of the events described above also means that either
an ApplicationReadyEvent or an ApplicationFailedEvent will be
published and the latter should never be published once the former
has been published.

Closes gh-11485

This commits improves the cache auto-configuration for Redis by looking
up a custom "RedisCacheConfiguration" bean that allows to take full
control over the `RedisCacheManager`.

Closes gh-11599

See gh-11428

Closes gh-11428

This commit adds SSL client Authentication support
to Reactor Netty and adds the relevant tests to
`AbstractReactiveWebServerFactoryTests` for all servers.

Fixes gh-11488

This commit applies `server.undertow.*` configuration properties
to Undertow when configured as a reactive web server.

See gh-11500

This commit applies `server.jetty.*` configuration properties
to Jetty when configured as a reactive web server.

It also removes some infrastructure support for Jetty 8, which
is not supported anymore in Spring Boot 2.0 (partial fix for
gh-11504).

See gh-11500

This commit applies most `server.tomcat.*` configuration
properties to Tomcat when set up as a reactive web server.

Some Servlet-specific properties are not applied:

* server.tomcat.additional-tld-skip-patterns
* server.tomcat.redirect-context-root
* server.tomcat.use-relative-redirects

Fixes gh-11334

Closes gh-11331

* pr/11591:
  Polish "Make GsonAutoConfiguration align with JacksonAutoConfiguration"
  Make GsonAutoConfiguration align with JacksonAutoConfiguration

Closes gh-11591

See gh-11591

Backport commit d439b737 to upgrade launch integration tests to
use docker-java 3.0.x.

Closes gh-11203

See gh-11023

Closes gh-11023

* pr/11587:
  Fix imports order for Checkstyle

Closes gh-11587

Closes gh-11022