* gh-17508:
  Remove unused java-statsd-client dependencies

Closes gh-17508

See gh-17508

* gh-17538:
  Polish "Hide loader classes from Tomcat's ServletContext resource paths"
  Hide loader classes from Tomcat's ServletContext resource paths

Closes gh-17538

See gh-17538

See gh-17538

Fixes gh-17555

Closes gh-17553

Previously, DeferredLinesWriter would collect MockMvc output from
every test that has executed. If a test eventually failed, the
output from every test up to including the one that had failed would
be output, rather than just the output for the test that has just
failed.

This commit clears the deferred lines after each test, thereby
ensuring that when a failure occurs only the lines from the failing
test are output.

Fixes gh-17551

Closes gh-17543

Fixes gh-17545

* pr/17496:
  Test the Gradle Plugin against Gradle 5.5.1

Closes gh-17496

See gh-17496

Setting the log file name to a random value in smoke tests
doesn't work because the logger context has already been initialized.

Using a random value for the logfile name caused
the logfile endpoint to return a 404 as the name
was resolved from the environment on every request.
This commit registers a bean for LogFile which is then
used by the logfile endpoint.

Fixes gh-17434

* gh-17480:
  Polish AbstractDependsOnBeanFactoryPostProcessor

Closes gh-17480

See gh-17480

* gh-16627:
  Polish "Set up MongoClient beans' dependencies by type rather than name"
  Set up MongoClient beans' dependencies by type rather than name

Closes gh-16627

See gh-16627

See gh-16627

* gh-17020:
  Polish "Allow depended on beans to be identified by type"
  Allow depended on beans to be identified by type

Closes gh-17020

See gh-17020

Prior to this commit, `AbstractDependsOnBeanFactoryPostProcessor`
could only identify depended on beans by name.

See gh-17020

Closes gh-17476

Fixes gh-17217

Closes gh-17446

Fixes gh-17465

Closes gh-17461

Closes gh-17445

Closes gh-17451

Closes gh-17449

Previously, if a user defined a MongoDbFactory bean but did not define
a client bean, MongoDataAutoConfiguration would back off leaving the
context without a MongoTemplate, etc.

This commit reworks the auto-configuration so that only the
auto-configuration of a MongoDbFactory is dependent on the existence
of a Mongo client bean. Auto-configuration of the other components
that depend on a MongoDbFactory will now continue in the absence of a
Mongo client bean.

Closes gh-17416

Closes gh-17428

Update `ValidationBindHandler` so that any non-null result returned by
the parent `onFailure` method triggers re-validation.

Fixes gh-17421

Previously, the context path was set to an empty string. The led to
Jetty logging a warning about an empty context path and then using
/ instead.

This commit avoids the warning while leaving the context path's end
result unchanged by setting the context path to /.

Closes gh-17399

Closes gh-17407