Test Terminal.exitStatus API

[Tyriar]

Refs: #62103

• macOS @sandy081
• linux @RMacfarlane
• windows @fiveisprime

Complexity: 3

---

• Use yo code to generate an extension
• Listen to terminal exit using the new Terminal.exitStatus API, onDidOpenTerminal and onDidCloseTerminal events are helpful or this. Test the following:
  • Before the terminal has exited (should be undefined)
  • Exiting explicitly by typing exit 1 or exit 0 (should be { code: 1 } or { code: 0 })
  • Exit by hitting trash icon (should be { code: undefined })
• Ensure docs make sense