Fix WFP 'branding' in the source code

Various things to do to move the source for WFP beyond the out-of-date 'EE 9' concept. It's fine to create separate subtask issues for these.

1) Various code references to 'EE 9', e.g. maven module descriptions, comments etc. Rename the 'wildfly-ee-9-parent' artifact id.

2) Rename the ee-9 dir to preview. (Discuss with Yeray first in case of any downstream effects.)

3) The hard one – the ts.ee9 and ts.bootable.ee9 profiles. Changing the properties used for these will break workflows, e.g. CI jobs and individual developer build habits. So this would require announcing the change and coordinating getting CI updated.