Closes gh-8112

See gh-8112

Closes gh-8032

Closes gh-7703

Update all `EmbeddedServletContainer` implementations to ensure that
the `start()` method can be called multiple times, with the second call
being ignored.

Fixes gh-8036

Update `Log4J2LoggingSystem` and `LogbackLoggingSystem` to ensure
that filters are removed when the `cleanUp` method is called. Prior
to this commit application failures would not remove the filter and
no log messages would appear.

The `LoggingApplicationListener` has also been updated since it
previously failed to handle `ApplicationFailureEvents`.

Finally `EventPublishingRunListener` and `DelegatingApplicationListener`
have been updated to deal with `null` parameters and to cope with
listener errors.

Fixes gh-7758

This reverts commit 70cd5c42.

See gh-8083

Closes gh-7774

Previously, AbstractEmbeddedServletContainerFactory detected an
exploded war by looking for `/WEB-INF/` in the path of its code
source's location. This failed on Windows due to the use of `\` rather
than `/` separators.

This commit updates AbstractEmbeddedServletContainerFactory to
uses the OS's separator rather than hardcoding `/`.

Closes gh-8100

Closes gh-8102

Closes gh-8086

Closes gh-8085

Closes gh-8084

Closes gh-8083

Closes gh-8082

Closes gh-8081

Closes gh-8080

Closes gh-8079

Closes gh-8078

Closes gh-69

See gh-7774

Closes gh-7652

* pr/8057:
  Fix entry in broken-initialization.factories

Closes gh-8057

Closes gh-7360

Closes gh-2753

* pr/8039:
  Indenting SpringApplication javadoc code

Closes gh-8039

Closes gh-8040

Closes gh-8033

Previously, when the ExpectedException JUnit rule was used with
FilteredClassPathRunner a LinkageError would occur if any of
ExpectedException's methods that take a Hamcrest Matcher were called.
This was due to the FilteredClassLoader delegating loading of
org.junit classes to its parent but not org.hamcrest classes. This
resulted in JUnit classes loading one version of the Hamcrest class
and the test class loading another.

This commit ensures that both the JUnit classes and the test class
use the same version of Hamcrest classes by also delegating the
loading of org.hamcrest classes to FilteredClassLoader's parent.

* pr/8030:
  Fix closing parentheses

Closes gh-8030

By default, `@DataJpaTest` (and `@AutoConfigureTestDatabase`) attempt to
replace any existing `DataSource` by an embedded one. Previously, if
there is was no embedded database on the classpath, the exception message
did not provide that context in the error message.

This commit clarifies the error message to conduct
`TestDatabaseAutoConfiguration` (that is replacing the existing
`DataSource`).

Closes gh-7797

Previously, TestRestTemplate would only apply the UriTemplateHandler
to Strings and not to URIs. When using the auto-configured
TestRestTemplate, this prevented relative URIs from being
made absolute using LocalHostUriTemplateHandler.

The commit updates TestRestTemplate to turn URIs into Strings before
passing them to the delegate RestTemplate. Turning them into Strings
ensures that the delegate calls the UriTemplateHandler.

Closes gh-7891

Previously, when DevTools' was used it would set the application
context's ResourceLoader and overwrite any custom ResourceLoader that
had been configured. On the rare occasion when the user had customized
the ResourceLoader this meant that the customization was lost and
certain resources would become unavailable.

This commit updates DevTools' ResourceLoader to delegate a custom
ResourceLoader if one has been configured. If one has not been
configured it delegates as before, i.e. to
WebApplicationContextResourceLoader for web applications and to
DefaultResourceLoader for all others apps.

Closes gh-8010