task: process output is not displayed in a terminal

[paul-marechal]

Description

This is different from #3791. In this case, we simply don't open a terminal when executing process tasks.

The only difference between shell and process tasks, as per VS Code, is the way arguments are processed and the program executed.

But both task types should display their output in the terminal.

There are very good chances that about any task type may want its output displayed in a terminal as well, but that's to be confirmed.

Reproduction Steps

Try executing the following task:

{
    "tasks": [
        {
            "label": "[Task] Echo a string",
            "type": "process",
            "cwd": "${workspaceFolder}",
            "command": "bash",
            "args": [
                "-c",
                "sleep 3 && echo 1 2 3"
            ]
        }
    ]
}

No terminal is opened to display the output, despite the sleep 3 command (to avoid the issue where short-lived tasks are unregistered too quickly from the process/task manager).

OS and Theia version: Ubuntu 16.04 Theia@11badc80598254e8c78a204b7b93c2368a300fe4