[dif] simplify autogen DIF templates by sharing typedefs

This partially addressed #8142 by sharing, rather than autogenerating,
duplicate common DIFs typedefs.

Signed-off-by: Timothy Trippel <ttrippel@google.com>
diff --git a/util/check_dif_statuses.py b/util/check_dif_statuses.py
index 7f7e32b..9f78a55 100644
--- a/util/check_dif_statuses.py
+++ b/util/check_dif_statuses.py
@@ -456,7 +456,7 @@
         print("WARNING: It is recommended to pass the --top-hjson switch to "
               "get a more accurate representation of the DIF progress. The "
               "list of IPs for which no DIF sources exist is unknown.")
-        shared_headers = ["dif_warn_unused_result"]
+        shared_headers = ["dif_base"]
         top_level = "top_earlgrey"
         difs = get_list_of_difs(difs_root_path, shared_headers)