Factory with Theia: implement branch checkout while cloning a project defined in the factory definition

[sunix]

Description

Part of import projects which is a subtask of #9074

Implement branch checkout while cloning a project defined in the factory definition (if a branch is specified). This is comming next after #9221 (clone of a project in factory).

      {
        "name": "che-theia-factory",
...
        "source": {
          "location": "https://github.com/eclipse/che-theia-factory-extension",
          "type": "git",
          "parameters": {
            "branch": "master"
          }
        },

source.parameters['branch'] is the branch to checkout

[sunix]

Fixed with initial contribution