Previously LOG_LEVEL_PATTERN and LOG_DATEFORMAT_PATTERN were not
consumed as system properties in log4j2.xml and log4j2-file.xml. As a
result, the logging.pattern.level and logging.pattern.dateformat
configuration properties, which are translated into the
LOG_LEVEL_PATTERN and LOG_DATEFORMAT_PATTERN system properties
respectively had no effect.

This commit updates the log4j2.xml and log4j2-file.xml config files to
consume LOG_LEVEL_PATTERN and LOG_DATEFORMAT_PATTERN as system
properties. When the system property is not set, the configuation falls
back to the default values specified in the config files. Tests for
both log4j2.xml and log4j2-file.xml to verify the behaviour have also
bean added.

Fixes gh-22983