Improve output log performance.

Added method to create a new line in RichTextLabel without adding an ItemNewline to the previous line. Previously, removing a line then adding a newline was adding unnecessary ItemNewline instances to the previous line, significantly the remove_line method.

scene/gui/rich_text_label.h

@@ -483,6 +483,8 @@ public:
 	void push_cell();
 	void pop();
 
+	void increment_line_count();
+
 	void clear();
 
 	void set_offset(int p_pixel);