Now that there is a separate log4j-core-java9 and log4j-core is a multi-release jar, we can move ProcessIdUtil out of log4j-api into log4j-core.
Hopefully this will fix LOG4J2-2038 and LOG4J2-2133.
[Android] Compilation error when using log4j 2.9.0
Log4J 2 appears incompatible with Android platform due to inclusion of Java 9 classes (class file version 53)
Create log4j-core-java9 module