Migration Guide for Eclipse 4.34

Migration guide for Eclipse 4.34

Done through https://github.com/eclipse-platform/eclipse.platform.releng.aggregator/pull/2543, https://github.com/eclipse-jdt/eclipse.jdt/pull/119 and https://github.com/eclipse-platform/www.eclipse.org-eclipse/pull/252