Use recommended client-side JPMS settings in the wildfly-core pom

The modular.jdk.args JPMS settings used in the core pom should include the full set of client-side recommended settings, as that param drives the test client. Doing this promotes having a consistent test environment.

The --add-opens=java.base/sun.security.ssl=ALL-UNNAMED setting currently there should be moved to elytron/pom.xml as the only use for it is for org.wildfly.extension.elytron.TlsTestCase, which runs with a config that explicitly declares an internal JDK class should be used.

This relates to WFWIP-467. Perhaps related to that or similar issues we will do more than what I describe here, but this is a simple basic step.