REORG: conn_stream: move conn-stream stuff in dedicated files

Move code dealing with the conn-streams in dedicated files.

src/ssl_sample.c

@@ -25,6 +25,7 @@
 #include <haproxy/arg.h>
 #include <haproxy/base64.h>
 #include <haproxy/buf-t.h>
+#include <haproxy/conn_stream.h>
 #include <haproxy/obj_type.h>
 #include <haproxy/openssl-compat.h>
 #include <haproxy/sample.h>