REORG: include: move stats.h to haproxy/stats{,-t}.h

Just some minor reordering, and the usual cleanup of call places for
those which didn't need it. We don't include the whole tools.h into
stats-t anymore but just tools-t.h.
diff --git a/src/peers.c b/src/peers.c
index 1d60e3f..c9d5735 100644
--- a/src/peers.c
+++ b/src/peers.c
@@ -30,12 +30,11 @@
 #include <haproxy/task.h>
 #include <haproxy/session-t.h>
 #include <haproxy/signal.h>
+#include <haproxy/stats-t.h>
 #include <haproxy/time.h>
 #include <haproxy/tools.h>
 #include <haproxy/thread.h>
 
-#include <types/stats.h>
-
 #include <proto/channel.h>
 #include <proto/cli.h>
 #include <haproxy/fd.h>