[Java] Add a default config file for log4j2. (ray-project#23225)

We add a default config file for java worker to make info logs are able to be printed before `Ray.init()` invoked.

java/runtime/src/main/resources/log4j2.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--NOTE: This configuration file is important, we shouldn't remove it.
+ In log4j2, if we don't specify the log level, the default value is error.
+ In our case that if we logged before `Ray.init()`, the logs will not printed.
+ -->
+<Configuration status="info" name="RayDefaultLog4j2ConfigBeforeInit">
+ <ThresholdFilter level="debug"/>
+
+ <Appenders>
+ <Console name="STDOUT" target="SYSTEM_OUT">
+ <PatternLayout pattern="%d{yyyy-MM-dd HH:mm:ss,SSS} %p %c{1} [%t]: %m%n"/>
+ <ThresholdFilter level="debug"/>
+ </Console>
+ </Appenders>
+
+ <Loggers>
+ <Root level="info">
+ <AppenderRef ref="STDOUT"/>
+ </Root>
+ </Loggers>
+
+</Configuration>