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

Closes gh-22143

Closes gh-22553

Closes gh-22551

* gh-22550:
  Disable extra scans for full profile.

Closes gh-22550

The extra scans were not disabled for the full profile, only the
regular profile.

See gh-22550