This commit ensures that a user provides a non-empty expression in
declarations of @DisabledIf.

Issue: SPR-14614

Issue: SPR-14636

Issue: SPR-13188

* ttddyy-SPR-14614:
  Revise @DisabledIf support for JUnit Jupiter
  Introduce @DisabledIf annotation for JUnit 5

- Extracted stand-alone DisabledIfCondition from the SpringExtension
  so that the condition is only evaluated when necessary.

- Simplified implementation of DisabledIfCondition.

- Overhauled and extended logging in DisabledIfCondition.

- DisabledIfCondition now throws an IllegalStateException if @DisabledIf
  is not present on the test element or if the expression does not
  evaluate to a String or Boolean.

- Each generated ConditionEvaluationResult now includes the actual
  expression in the default reason.

- @DisabledIf is now auto-configured to be evaluated by the
  DisabledIfCondition since it is now meta-annotated with
  @ExtendWith(DisabledIfCondition.class)

- Overhauled documentation for @DisabledIf and provided standard
  examples as well as an @DisabledOnMac annotation to demonstrate
  support for custom composed annotations.

Issue: SPR-14614

This commit introduces @DisabledIf annotation that takes SpEL as a
condition.  The condition is evaluated at run time whether to disable
JUnit 5 (Jupiter) test method/class.

Issue: SPR-14614

Issue: SPR-14632

(cherry picked from commit 430180aa)

When using a `RestTemplate` instance within a Spring MVC application,
client exceptions may propagate in the MVC stack and can be wrongly
mapped by server `ExceptionHandlers`, leading to a wrong HTTP response
sent to the MVC client.

The `RestTemplate` instance uses `HttpMessageConverter` to decode
the remote service responses; and when those fail decoding an HTTP
response, they can throw an `HttpMessageNotReadableException`. That
exception then bubbles up through the `HttpMessageConverterExtractor`,
`RestTemplate` and the whole MVC stack, later mapped to HTTP 400
responses, since those exceptions can also be throws by the server stack
when the incoming requests can't be deserialized.

This commit wraps all `IOException` and `HttpMessageNotReadableException`
instances thrown by the extractor into `RestClientException`` instances.
It's now easier to consistently handle client exceptions and avoid such
edge cases.

Issue: SPR-13592

This change adds support for a target type in JsonPath assertions in
Spring MVC Test.

The existing assertValue(String expression, Object expectedValue)
transparently falls back on using an alternative JsonPath API that
allows specifying the target type to coerce to.

There is also a new overloaded method
assertValue(String expression, Matcher<T> matcher, Class<T> targetType)
for use with Hamcrest matchers where the target type can be specified.

Issue: SPR-14498

HttpEntityMethodProcessor should not throw IllegalArgumentExceptions for
invalid If-None-Match headers.

For those cases, this commit makes sure that both
`HttpEntityMethodProcessor` and `ServletWebRequest` have a consistent
behavior and stop processing the request as conditional and leave the
handler handle it.

Issue: SPR-14559

Issue: SPR-14492

This reverts commit bbd59939.

This commit also sets the test source encoding to UTF-8.

Issue: SPR-14547

This commit sorts `ClientHttpRequestInterceptor`s when those are set in
`InterceptingHttpAccessor` (which `RestTemplate` extends from).

Interceptors can now be annotated with `@order` or implements `Ordered`
to reflect their order of execution for each request.

Issue: SPR-13971

Added getHost/setHost to HttpHeaders, returning/taking a
InetSocketAddress.

This commit adds support for HTTP header field parameters encoding, as
described in RFC5987.
Note that the default implementation still relies on US-ASCII encoding,
as the latest rfc7230 Section 3.2.4 says that:

> Newly defined header fields SHOULD limit their field values to
  US-ASCII octets

Issue: SPR-14547

DefaultListableBeanFactory does not trigger early candidate creation ahead of primary bean selection

Issue: SPR-14611

Issue: SPR-14626

Issue: SPR-14625

Issue: SPR-14624

Issue: SPR-14609
(cherry picked from commit ab686732)

Issue: SPR-14609

Issue: SPR-7549

Includes optimized method/header resolution in CorsConfiguration.

Issue: SPR-14617

Prior to this commit, extracting an HTTP response with an empty body
and no Content-Type header using the WebClient would:

* trigger the use of the Jackson2JsonDecoder
* throw a NoSuchElementException because of the use of `Flux.single()`

This commit changes this behavior to `Flux.singleOrEmpty()` to avoid
throwing exceptions for empty Flux instances.

Issue: SPR-14582

Issue: SPR-14607

Issue: SPR-14616

Default ClientOptions enable SSL support.

Issue: SPR-14593

* reactor-core 3.0.1.BUILD-SNAPSHOT
* reactor-netty 0.6.0.BUILD-SNAPSHOT

This commit ensures that JUnit XML reports are generated in the old
Gradle 2.x location for all tests in the spring-test module.

Issue: SPR-14569

Issue: SPR-14569

Since the upgrade to Gradle 3, our Bamboo build is failing because it
can't find test reports "at the usual location".

This commit restores the location that Gradle 2 was using until we
upgrade to a version of Bamboo that supports it.

Issue: SPR-14569

Fix the build to work with reactor-core-3.0.0.RELEASE