Shell module

[jnovikov]

Introduce shell module.

This PR introduces new module that allow to spawn interactive shell.
Module supports actions for starting and stopping shells. Module supports multiple shells spawned on single agent.

Implementation details:

• Module uses minified version of xterm.js library to emulate client-side terminal. This library is distributed under MIT license.
• Client side part of the module implemented using pseudo terminals:
• Windows: WinPTY library is used. Library is distributed under MIT license. Module uses DLL + Agent binary downloaded from WinPTY releases page.
• MacOS: BSD functions to spawn PTTY are used.
• Linux: raw system calls are used because BSD functions are not available without installing special headers.

How to test the Change

You can import module and try to interact with the spawned shell.

Changelog Entry

Added - New "shell" module. Module that allows to spawn interactive shell on agents.

Checklist:

• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests pass.