Scrolling to the bottom sometimes makes the terminal jump under the file explorer

[alexdima]

Testing #6654

This is sort of what I did:

• cd .\src\vs\languages\typescript\common\lib
• node generate.js
• cls
• scroll down
  

[Tyriar]

From @kieferrm in #6846

OS: Windows

1. open the built-in terminal
2. run command that produces a bunch of output such as 'npm list' or cat a file
3. try to scroll up to reveal text that was already scrolled out of sight
   -> content is scrolled to the left (and then gets stuck)
   -> there is no reliable way to get the terminal back into a 'normal' state; sometime Enter works, sometimes not

Here is a screen recording.

[Tyriar]

This could very well be fixed with transition to xterm.js, need to wait for repros in insiders