Find dialog (Ctrl+Shift+F), center the found string vertically

# Description of the new feature/enhancement

When the find dialog is used, center the found string vertically in the terminal.

# Proposed technical implementation details (optional)

I'm often interested in the few lines before the search string and sometimes the found string is behind the dialog itself. Centering it vertically would help in both cases.

No files or tests are named in the issue. Start with the Ctrl+Shift+F find dialog in Windows Terminal and trace how a found string is positioned; the work is done when the found string is vertically centered in the terminal and remains visible rather than being covered by the dialog.

Written by the indexing model from the issue text.