Remove jre images and bundles

Since JDK 9 and modules, the idea of a prebuilt JRE is no longer providing much value. The idea is rather that you link together an image with the modules you actually need, together with your application. For this reason oracle will no longer ship JRE images that differ content wise to the JDK image in JDK 11 and we would like to remove them from OpenJDK as well.

If not accepted by the community, we will at least make building them more optional by removing them from the default images and bundles targets.