Replaced with java.util.Objects.hashCode(Object)/equals(Object, Object)
which has existed since Java 1.7.

This does not yet remove the hashCode entrypoints but deprecates them.
Platform uses of ObjectUtils.hashCode variants has been removed however
but some can still exist in other projects.

Some org.simantics.utils.ObjectUtils.objectEquals uses still exist after
these changes.

gitlab #898