Remove ununsed JVM API JVM_GetModuleByPackageName()

Remove JVM_GetModuleByPackageName() because it is not called except for by its own test, JVMGetModuleByPkgName.java.

Removing it involves removing all references to it by the JVM and JDK, removing its internal implementation function Modules::get_module_by_package_name(), and removing its test.