Adopt VT extension "Unscrolling the screen" from Kitty

# Description of the new feature/enhancement

Kitty has recently shipped an awesome VT extension to the SD (Pan up) escape code from the VT-420 terminal to tackle the issues with text being lost under the cursor. I'd like to see this added in Windows Terminal as well. See https://sw.kovidgoyal.net/kitty/protocol-extensions.html#unscrolling-the-screen. As there have been several issues raised in the past surrounding this issue, this appears to be the perfect solution to prevent further issues from being raised about it. Also, since Windows Terminal adopted private extensions from ConEmu to address other issues, I see no reason why we can't also adopt some of Kitty's protocol extensions as well.

# Proposed technical implementation details (optional)

Start with the Kitty protocol-extensions page linked in the issue, focusing on the “Unscrolling the screen” SD (Pan up) escape code. Since no Windows Terminal file or test is named, locate the existing VT-420 SD handling and determine the compatibility and testing scope; done means the extension works as proposed without regressing terminal scrolling.

Written by the indexing model from the issue text.