patch 8.2.2803: flicker when the popup menu has an info popup

Problem:    Flicker when the popup menu has an info popup.
Solution:   Avoid drawing over the popup when it's going to be redrawn in the
            same position. (closes #8131)  Also avoid redrawing the scrollbar.
diff --git a/src/drawscreen.c b/src/drawscreen.c
index 4a716b2..bb0d887 100644
--- a/src/drawscreen.c
+++ b/src/drawscreen.c
@@ -93,6 +93,7 @@
     int		gui_cursor_row = 0;
 #endif
     int		no_update = FALSE;
+    int		save_pum_will_redraw = pum_will_redraw;
 
     // Don't do anything if the screen structures are (not yet) valid.
     if (!screen_valid(TRUE))
@@ -276,6 +277,11 @@
     }
 #endif
 
+    if (pum_redraw_in_same_position())
+	// Avoid flicker if the popup menu is going to be redrawn in the same
+	// position.
+	pum_will_redraw = TRUE;
+
     // Go from top to bottom through the windows, redrawing the ones that need
     // it.
 #if defined(FEAT_SEARCH_EXTRA) || defined(FEAT_CLIPBOARD)
@@ -321,7 +327,9 @@
 #if defined(FEAT_SEARCH_EXTRA)
     end_search_hl();
 #endif
+
     // May need to redraw the popup menu.
+    pum_will_redraw = save_pum_will_redraw;
     pum_may_redraw();
 
     // Reset b_mod_set flags.  Going through all windows is probably faster