Bug 570941 - Update org.eclipse.core.tests.resources to Java 11

We require Java 11 anyway for the SDK to run and this would allow us to
modernize the
resource tests.

Change-Id: I77a95ebe5a8b833c40134bb59efc6fa834fd36d0
Signed-off-by: Lars Vogel <Lars.Vogel@vogella.com>