patch 9.2.0127: line('w0') and line('w$') return wrong values in a terminal

patch 9.2.0127: line('w0') and line('w$') return wrong values in a terminal

Problem:  In a terminal window, line('w0') and line('w$') return wrong
          values instead of the first and last visible line number,
          because a terminal buffer does not go through the normal
          redraw path that updates w_topline and w_botline (ubaldot).
Solution: Before computing w0 and w$, sync the terminal contents to the
          buffer by calling may_move_terminal_to_buffer() so that
          w_topline and w_botline are correctly updated.

fixes:  #19585
closes: #19615

supported by AI claude.

Signed-off-by: Christian Brabandt <cb@256bit.org>