Fix some NS drawing issues (bug#32932)

Fix some NS drawing issues (bug#32932)

* src/nsterm.m (ns_clip_to_rect):
(ns_reset_clipping): Remove gsaved variable and associated code.
(ns_flush_display): Remove function.
(ns_copy_bits): use translateRectsNeedingDisplayInRect:by: to copy any
pending drawing actions along with the image.
([EmacsView windowWillResize:toSize:]): Remove unneeded call.
([EmacsView drawRect:]): Remove redundant call to ns_clear_frame_area,
and optimize the exposed rectangles.
(ns_draw_window_cursor): Remove unneeded disabling of screen updates.