Bump to version of k3 including StepCommand return null fix

[ebousse]

Description

Bump to the latest version of K3 that includes the support for all kind of StepCommand (ie. result being void, null or an object)

Changes

Adapt the engine to the new return structure (ie. List)

Companion Pull Requests

• https://github.com/eclipse/gemoc-studio/pull/284
• https://github.com/eclipse/gemoc-studio-modeldebugging/pull/229
• https://github.com/eclipse/gemoc-studio-execution-java/pull/30
• https://github.com/eclipse/gemoc-studio-execution-moccml/pull/74