Migration of eclipse/gemoc-studio* to eclipse-gemoc/gemoc-studio*

## Bug description

Eclipse foundation management of github repositories changed from one monolithic organisation to smaller project organisations. cf. https://gitlab.eclipse.org/eclipsefdn/helpdesk/-/issues/3571

GEMOC studio is also moving: https://gitlab.eclipse.org/eclipsefdn/helpdesk/-/issues/4964

This ticket traces the various actions required:

- [x] update of the CI integration repository https://github.com/gemoc/gemoc-studio-eclipse-integration
- [x] check if some of our jenkins jobs needs an update https://ci.eclipse.org/gemoc
- [x] update project page https://projects.eclipse.org/projects/modeling.gemoc
- [ ] update gemoc.org web site https://gemoc.org/studio.html
- [ ] send an email to all gemoc user via mailing list
- [ ] (optional) evaluate opportunity to use the new `github self-service` feature (https://www.eclipse.org/projects/handbook/#resources-github-self-service) to see if it helps moving the integration repository in this new organisation (ie. https://github.com/gemoc/gemoc-studio-eclipse-integration)