CLEANUP: stream: rename "csf" and "csb" to "scf" and "scb"

These are the stream connectors, let's give them consistent names. The
patch is large (405 locations) but totally trivial.
diff --git a/src/ssl_sock.c b/src/ssl_sock.c
index 1c614d2..6578e91 100644
--- a/src/ssl_sock.c
+++ b/src/ssl_sock.c
@@ -7885,7 +7885,7 @@
 	struct stconn *cs;
 
 	conn = objt_conn(sess->origin);
-	cs = s->csf;
+	cs = s->scf;
 
 	if (conn && cs) {
 		if (conn->flags & (CO_FL_EARLY_SSL_HS | CO_FL_SSL_WAIT_HS)) {