Call all ewmh_update_* functions together when necessary

The testcase is changed because it was actually incorrect. Easy to
verify because:
> _NET_CURRENT_DESKTOP
> …
> The index of the current desktop. This is always an integer between 0
> and _NET_NUMBER_OF_DESKTOPS - 1.

Fixes #3696.
Also updates the viewports.

Finally, fixes an issue with _NET_CURRENT_DESKTOP not being updated
after a workspace rename. Example:
- workspaces 1, 2, 3
- rename workspace 1 to 5
- All workspaces changed their index but _NET_CURRENT_DESKTOP was not
updated

include/ewmh.h

@@ -11,6 +11,12 @@
 
 #include <config.h>
 
+/**
+ * Updates all the EWMH desktop properties.
+ *
+ */
+void ewmh_update_desktop_properties(void);
+
 /**
  * Updates _NET_CURRENT_DESKTOP with the current desktop number.
  *
@@ -20,24 +26,6 @@
  */
 void ewmh_update_current_desktop(void);
 
-/**
- * Updates _NET_NUMBER_OF_DESKTOPS which we interpret as the number of
- * noninternal workspaces.
- */
-void ewmh_update_number_of_desktops(void);
-
-/**
- * Updates _NET_DESKTOP_NAMES: "The names of all virtual desktops. This is a
- * list of NULL-terminated strings in UTF-8 encoding"
- */
-void ewmh_update_desktop_names(void);
-
-/**
- * Updates _NET_DESKTOP_VIEWPORT, which is an array of pairs of cardinals that
- * define the top left corner of each desktop's viewport.
- */
-void ewmh_update_desktop_viewport(void);
-
 /**
  * Updates _NET_WM_DESKTOP for all windows.
  * A request will only be made if the cached value differs from the calculated value.