ui/console-vc: report cursor position in the screen not in the scroll buffer

ui/console-vc: report cursor position in the screen not in the scroll buffer

The format of the CSI cursor position report is `ESC[row;columnR`,
where `row` is a row of a cursor in the screen, not in the scrollback
buffer. What's the difference? Let's say the terminal screen has 24
lines, no matter how long the scrollback buffer may be, the last line
is the 24th.

For example the following command can be executed in xterm on the last
screen line:

   $ echo -en '\e[6n'; IFS='[;' read -sdR _ row col; echo $row:$col
   24:1

It shows the cursor position on the current screen and not relative
to the backscroll buffer.

Before this change the row number was always increasing for the QEMU
VC and represents the cursor position relative to the backscroll
buffer.

Signed-off-by: Roman Penyaev <r.peniaev@gmail.com>
Cc: "Marc-André Lureau" <marcandre.lureau@redhat.com>
Cc: qemu-devel@nongnu.org
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-ID: <20250226075913.353676-4-r.peniaev@gmail.com>