Update devfilev2 sample projects to refer to udi-rhel8 images

After 2.15 is released, update devfilev2 sample projects to refer to udi-rhel8 images instead of obsolete plugin-java8 and plugin-java11 from 2.15

See https://github.com/crw-samples/ for list of affected projects; then look for the devfilev2 branches.

Note that the terminal name has changed from "maven" to "tools" so we need to update the instructions in the Log into deployment cluster commands - see https://github.com/redhat-developer/devspaces/pull/733/commits/e79c391dc0fad99dfa9d4a28fbd7ad56a51c5b7c for how this would be done if we still used the v1 devfiles.