ui/console: rename vga_ functions with qemu_console_

They are not specific to VGA. Let's use the object type name as prefix
instead, to avoid confusion.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20230830093843.3531473-38-marcandre.lureau@redhat.com>