[DevTask] Remove terminal.restore API

[webfiltered]

Terminal keeps an array of raw output strings as the terminal buffer, and restore() returns the raw strings when requested. They are fed via IPC on a delay to the frontend. As we are using a full pty, this design causes various issues.

We should remove this raw buffer and instead utilise the pty buffer to handle save/restore - thus removing the need to replay every control character at potentially different width/height.