See gh-11727

Closes gh-11741

Closes gh-11740

Closes gh-11739

Closes gh-11738

Closes gh-11737

Closes gh-11736

Closes gh-11735

Closes gh-11734

Closes gh-11733

Closes gh-11732

Closes gh-11731

Closes gh-11730

Closes gh-11729

Closes gh-11728

Closes gh-11727

Closes gh-11726

This commit makes sure that `CharacterEncodingFilter` is ordered with
the `Ordered.HIGHEST_PRECEDENCE` and that other filters, potentially
reading the request body, are ordered after.

In this particular case, both `WebMvcMetricsFilter` and
`ErrorPageFilter` are now ordered at `Ordered.HIGHEST_PRECEDENCE + 1` to
avoid cases where the request body is read before the encoding
configuration is taken into account.

Closes gh-11607

This commit adds a new `spring-boot-configuration-analyzer` module that
can be added to any app to analyze its environment on startup.

Each configuration key that has a matching replacement is temporarily
transitioned to the new name with a `WARN` report that lists all of
them.

If the project defines configuration keys that don't have a replacement,
an `ERROR` report lists them with more information if it is available.

Closes gh-11301

* pr/11716:
  Manage dependencies for kotlin-stdlib-jdk7/8

As explained in the "Split package compatibility" section of
https://blog.jetbrains.com/kotlin/2017/09/kotlin-1-2-beta-is-out/
kotlin-stdlib-jdk7 and kotlin-stdlib-jdk8 are the recommended
dependencies to use with Kotlin 1.2 for Java 9+ compatibility.

Closes gh-11716

* pr/11674:
  Use the platform-specific line separator

Closes gh-11674

* pr/11692:
  Add missing null checks and volatile keyword

Closes gh-11692

Closes gh-9979

Closes gh-11712

Add `@ControllerEndpoint` and `@RestControllerEndpoint` annotations that
can be used to develop a Spring-only request mapped endpoint. Both
Spring MVC and Spring WebFlux are supported.

This feature is primarily for use when deeper Spring integration is
required or when existing Spring Boot 1.5 projects want to migrate to
Spring Boot 2.0 without re-writing existing endpoints. It comes at the
expense of portability, since such endpoints will be missing from
Jersey.

Fixes gh-10257

Create a `PathMappedEndpoint` interface that allows any `ExposedEndpoint`
to provide root path details. The `EndpointPathResolver` interface has
been renamed to `PathMapper` and is now only used during endpoint
discovery.

`EndpointPathProvider` has been replaced with `PathMappedEndpoints`
which simply finds relevant path mapped endpoints.

Fixes gh-10985

Refactor several areas of the actuator endpoint code in order to make
future extensions easier. The primary goal is to introduce the concept
of an `ExposableEndpoint` that has technology specific subclasses and
can carry additional data for filters to use. Many other changes have
been made along the way including:

* A new EndpointSupplier interface that allows cleaner separation of
  supplying vs discovering endpoints. This allows cleaner class names
  and allows for better auto-configuration since a user can choose to
  provide their own supplier entirely.

* A `DiscoveredEndpoint` interface that allows the `EndpointFilter`
  to be greatly simplified. A filter now doesn't need to know about
  discovery concerns unless absolutely necessary.

* Improved naming and package structure. Many technology specific
  concerns are now grouped in a better way. Related concerns are
  co-located and concepts from one area no longer leakage into another.

* Simplified `HandlerMapping` implementations. Many common concerns have
  been pulled up helping to create simpler subclasses.

* Simplified JMX adapters. Many of the intermediary `Info` classes have
  been removed. The `DiscoveredJmxOperation` is now responsible for
  mapping methods to operations.

* A specific @`HealthEndpointCloudFoundryExtension` for Cloud Foundry.
  The extension logic used to create a "full" health endpoint extension
  has been made explicit.

Fixes gh-11428
Fixes gh-11581