Missing Xtext integration during ALE execution

[dvojtise]

In the Java engine, if the language has an xtext representation, when clicking on the Debug Stack view, the xtext editor opens at the line involved by the instruction. The line is also highlighted.

We should add this in ALE engine too.

[dvojtise]

code for the javaEngine is here https://github.com/eclipse/gemoc-studio-modeldebugging/blob/master/java_execution/java_engine/plugins/org.eclipse.gemoc.execution.sequential.javaengine.ui/src/org/eclipse/gemoc/execution/sequential/javaengine/ui/launcher/GemocSourceLocator.java