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

This one is particularly tricky to move because everyone uses it
and it depends on a lot of other types. For example it cannot include
arg-t.h and must absolutely only rely on forward declarations to avoid
dependency loops between vars -> sample_data -> arg. In order to address
this one, it would be nice to split the sample_data part out of sample.h.
diff --git a/contrib/mod_defender/defender.h b/contrib/mod_defender/defender.h
index 088416e..59241b2 100644
--- a/contrib/mod_defender/defender.h
+++ b/contrib/mod_defender/defender.h
@@ -12,7 +12,7 @@
 #ifndef __DEFENDER_H__
 #define __DEFENDER_H__
 
-#include <types/sample.h>
+#include <haproxy/sample-t.h>
 
 struct defender_request {
 	struct sample clientip;