* on_scrollback_option_changed renamed to adjust_scrollback. The
function name did not correspond to what it was doing. It is
called unconditionally in every refresh of the terminal
unrelated if the scrollback option was changed.
* new on_scrollback_option_changed function, which calls
refresh_terminal, which then calls adjust_scrollback
* terminal_check_size is not the appropriate function to call when the
option is changed since it only conditionally adjusts the scrollback.
Use the new on_scrollback_option_changed
fixes#15477fixes#11811
916d848049