Test: Terminal renderer extension API

[Tyriar]

#46192

• macOS @mjbvz
• Linux @jrieken
• Windows @dbaeumer

Complexity: 4

A new proposed extension API was added that lets extensions completely control what is visible within the terminal. This is done by created a TerminalRenderer which is a special terminal that instead of having a process is driven by an extension. Note that all TerminalRenderers also have Terminal objects associated with them.

Please read the API:

https://github.com/Microsoft/vscode/blob/d88b3dd55be626154bf1d43c6d8570e02b4a32bb/src/vs/vscode.proposed.d.ts#L383

And look at the extension samples: https://github.com/Microsoft/vscode-extension-samples/tree/master/terminal-sample

And experiment with the API and see if everything works as expected