Log4J2 enables its shutdown hook by default. When the JVM is exiting,
this creates a race between logging that happens during the
application context being closed and Log4J2 being shut down such that
the logging is lost.

This commit updates SpringBootConfigurationFactory so that it
produces a custom sub-class of DefaultConfiguration that disables the
shutdown hook by default. In addition to solving the problem described
above, this also aligns the Log4J2 logging system with the
logging.register-shutdown-hook property which defaults to false.

Closes gh-11360