Closes gh-22596

Closes gh-20408

Closes gh-22592

Closes gh-20896

Closes gh-22589

Closes gh-21696

Closes gh-22587

Closes gh-22278

Closes gh-22585

Previously, ignoring invalid fields would cause the failure for an
unknown field to be ignored, irrespective of the ignoreUnknownFields
attribute on `@ConfigurationProperties`.

This commit updates the NoUnboundElementsBindHandler to ensure that
any UnboundConfigurationPropertiesException is thrown rather than
being ignored when the handler has been wrapped by an
IgnoreErrorsBindHandler.

Fixes gh-22308

Closes gh-22583

The fix for gh-20916 updated DefinitionsParser so that the
ResolvableType for each MockBean or SpyBean field included the
implementation class from which the field was found. Where the field
was declared with a variable generic signature that was made constant
by its implementation class, this allowed the correct concrete type to
be determined. It also had the unintended side-effect of preventing two
test classes with identical `@MockBean` and `@SpyBean` configuration
from sharing a context as the resolvable types for their mock and spy
bean fields would now be different.

This commit updates DefinitionsParser to only include the
implementation class in the ResolvableType if the field's generic type
is variable. For cases where it is not variable, this restores the
behaviour prior to the fix for gh-20916.

Fixes gh-22566

Closes gh-22580

Previously, background pre-init was started in response to the
application starting event. This meant that it would be running while
the logging turbo filter was in place and was rejecting all logging.
As a result, any logging performed during pre-init would be lost.

This commit changes background pre-init so that it is now started
in response to the application environment prepared event. By this
point, the logging turbo filter has been removed as the logging levels
have been configured from the environment.

Closes gh-21897

Closes gh-22578

Previously, only UndertowOptions was used as the source of options for
both server and socket options, but it only contains server options.
As a result, attempting to configure any socket options defined by
XNIO's Options class would fail.

This commit updates the property-based configuration of options to use
UndertowOptions as the source for server options and XNIO's Options as
the source for socket options.

Fixes gh-22502

Closes gh-22576

Fixes gh-22530

Closes gh-22574

Closes gh-21868

This commit fixes the auto-configuration of the Couchbase caching
support by configuring the cache once Spring Data Couchbase has gotten
a chance to be processed.

Closes gh-22542

Closes gh-22563

* gh-22555:
  Polish "Add generated-snippets as output to test goal"
  Add generated-snippets as output to test goal

Closes gh-22555

See gh-22555

The generated snippets were not declared as an output to the
`spring-boot-actuator-autoconfigure` test goal so when the test was
pulled from the cache, it did not contain the `generated-snippets`
directory. This directory is required as an input to the Asciidoctor
plugin.

See gh-22555

Closes gh-22560