api: Add FUNC_ATTR_DEFERRED attribute to a number of functions

Any function that can directly mutate the screen or execute vimscript had the
attribute applied.

src/nvim/api/window.c

@@ -52,6 +52,7 @@ ArrayOf(Integer, 2) window_get_cursor(Window window, Error *err)
 /// @param pos the (row, col) tuple representing the new position
 /// @param[out] err Details of an error that may have occurred
 void window_set_cursor(Window window, ArrayOf(Integer, 2) pos, Error *err)
+  FUNC_ATTR_DEFERRED
 {
   win_T *win = find_window_by_handle(window, err);
 
@@ -111,6 +112,7 @@ Integer window_get_height(Window window, Error *err)
 /// @param height the new height in rows
 /// @param[out] err Details of an error that may have occurred
 void window_set_height(Window window, Integer height, Error *err)
+  FUNC_ATTR_DEFERRED
 {
   win_T *win = find_window_by_handle(window, err);
 
@@ -154,6 +156,7 @@ Integer window_get_width(Window window, Error *err)
 /// @param width the new width in columns
 /// @param[out] err Details of an error that may have occurred
 void window_set_width(Window window, Integer width, Error *err)
+  FUNC_ATTR_DEFERRED
 {
   win_T *win = find_window_by_handle(window, err);
 
@@ -199,6 +202,7 @@ Object window_get_var(Window window, String name, Error *err)
 /// @param[out] err Details of an error that may have occurred
 /// @return The old value
 Object window_set_var(Window window, String name, Object value, Error *err)
+  FUNC_ATTR_DEFERRED
 {
   win_T *win = find_window_by_handle(window, err);
 
@@ -234,6 +238,7 @@ Object window_get_option(Window window, String name, Error *err)
 /// @param value The option value
 /// @param[out] err Details of an error that may have occurred
 void window_set_option(Window window, String name, Object value, Error *err)
+  FUNC_ATTR_DEFERRED
 {
   win_T *win = find_window_by_handle(window, err);