REORG: rename cs_utils.h to sc_strm.h

This file contains all the stream-connector functions that are specific
to application layers of type stream. So let's name it accordingly so
that it's easier to figure what's located there.

The alphabetical ordering of include files was preserved.
diff --git a/src/ring.c b/src/ring.c
index 873d0d6..d39d8b6 100644
--- a/src/ring.c
+++ b/src/ring.c
@@ -24,8 +24,8 @@
 #include <haproxy/buf.h>
 #include <haproxy/cli.h>
 #include <haproxy/conn_stream.h>
-#include <haproxy/cs_utils.h>
 #include <haproxy/ring.h>
+#include <haproxy/sc_strm.h>
 #include <haproxy/thread.h>
 
 /* context used to dump the contents of a ring via "show events" or "show errors" */