scripted-diff: test: Rename send_message to send_without_ping

send_message only drops the bytes in a buffer and a sync is needed to
avoid intermittent test issues. Change the name of the method to make
this more apparent during review.

-BEGIN VERIFY SCRIPT-
 sed -i 's/send_message(/send_without_ping(/g' $( git grep -l 'send_message(' )
-END VERIFY SCRIPT-

test/functional/README.md

@@ -183,7 +183,7 @@ way is the use the `profile_with_perf` context manager, e.g.
 with node.profile_with_perf("send-big-msgs"):
     # Perform activity on the node you're interested in profiling, e.g.:
     for _ in range(10000):
-        node.p2ps[0].send_message(some_large_message)
+        node.p2ps[0].send_without_ping(some_large_message)
 ```
 
 To see useful textual output, run