[releng] Replace neon.papyrusnightly target with 2022-03

- Replace target definition for neon-papyrusnightly with 2022-03
- Remove neon target definition
- Use own releng configuration file instead of outdated components
  => switch to OpenJDK 11 as compiler, newer version of tycho, ...
- Switch to Java-11 in all plugins
- Add missing imports to xtext editors (no longer re-exported by Papyrus)

Signed-off-by: Ansgar Radermacher <ansgar.radermacher@cea.fr>
Change-Id: I47b90b741e21a37bdcf83e858ea290f33d0ca662