Test: terminal flow control

[meganrogge]

Refs #113827

• wsl
• ssh
• web

Complexity: 4

Authors: @Tyriar, @meganrogge

---

Background
When the terminal produces a lot of data, the flow control mechanism is designed to prevent node-pty and its process from getting too far ahead of xterm.js.

Action:

• Turn on the flow control setting, terminal.flowControl
• Test with terminal.integrated.serverSpawn on and off
• Run programs in the terminal that produce a lot of data, for example:

- yes
- while true; do echo test; done
- base64 /dev/urandom

Expectation::
The terminal doesn't disconnect and the UI doesn't slow down.

[Tyriar]

/duplicate #114377