Use custom docker image for building the studio on the CI

[dvojtise]

This PR contributes a new docker images that is based on https://github.com/eclipse-cbi/jiro/tree/master/jenkins-agent-images/migration-fat-agent

this migration-fat-agent is the image used when using

agent   {  
      kubernetes {
        label 'migration'
      }
    }

in the jenkins file

This modified image allows to:

• remove some useless tool in the image
• add graphviz: fix Figures broken in the development section of the documentation #151
• add ffmpeg and tmux (in order to try to capture video of the x display of tests)

the docker image is deployed https://hub.docker.com/repository/docker/gemoc/gemoc-jenkins-fat-agent in order to be used by the jenkinsfile (see https://github.com/gemoc/gemoc-studio-eclipse-integration )

[dvojtise]

The new image combined with an updated jenkinsfile allows to:

• fix the broken dev figures (see Figures broken in the development section of the documentation #151)
• contribute to flaky test analysis (Flaky tests #123) by adding a h264 video of the run of all system tests (recorded in lastSuccessfulBuild/artifact/gemoc-studio/dev_support/full_compilation/target/ )
• fix Using docker/kubernetes container to better control build environment #127 by fully controling the docker image on the CI

The jenkins also adds a global timeout and a system test timeot in order to prevent freezing all GEMOC build in case of hanging job.