console2: configure children process columns

[brig]

Allows configuring child process table columns within a project configuration:

{
  "ui": {
    "childrenProcessList": [
      {
        "builtin": "status"
      },
      {
        "builtin": "instanceId"
      },
      {
        "source": "meta.myColumn",
        "caption": "myColumn",
        "searchType": "equals",
        "searchValueType": "string"
      },
      {
        "builtin": "createdAt"
      },
      {
        "builtin": "lastRunAt"
      }
    ]
  }
}