Improve ICU4J build/release for maven repository

ICU4J build uses appache maven ant tasks http://maven.apache.org/ant-tasks/ to publish assets to OSSRH staging repository. The maven ant tasks component is recently retired, and you cannot get the jar from Apache any more.

This ticket is created for investigating apache maven ant tasks to something else (this is rather urgent), or migrating ICU4J ant build to modern build framework such as maven / gradle.