Polish Undertow access logs contribution

- Apply project’s code formatting and conventions
 - Don’t use the IO and worker thread configuration when creating the
   worker for the AccessLogReceiver. The IO and worker thread
   configuration is for HTTP request processing and a worker in its
   default configuration should be sufficient for the access log
   receiver.
 - Don’t use a temporary directory as the default for the access log
   directory. A temporary directory makes (some) sense for Tomcat as it
   requires a directory for its basedir. Undertow has no such
   requirement and using a temporary directory makes it hard to locate
   the logs. The default has been updated to a directory named logs,
   created in the current working directory.
 - Document the new properties in the application properties appendix

Closes gh-3014

spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -95,6 +95,9 @@ content into your application; rather pick only the properties that you need.
 	server.tomcat.max-http-header-size= # maximum size in bytes of the HTTP message header
 	server.tomcat.max-threads = 0 # number of threads in protocol handler
 	server.tomcat.uri-encoding = UTF-8 # character encoding to use for URL decoding
+	server.undertow.access-log-enabled=false # if access logging is enabled
+	server.undertow.access-log-pattern=common # log pattern of the access log
+	server.undertow.access-log-dir=logs # access logs directory
 
 	# SPRING MVC ({sc-spring-boot-autoconfigure}/web/WebMvcProperties.{sc-ext}[WebMvcProperties])
 	spring.mvc.locale= # set fixed locale, e.g. en_UK