REORG: include: split common/regex.h into haproxy/regex{,-t}.h

Regex are essentially included for myregex_t but it turns out that
several of the C files didn't include it directly, relying on the
one included by their own .h. This has been cleanly addressed so
that only the type is included by H files which need it, and adding
the missing includes for the other ones.
diff --git a/include/types/checks.h b/include/types/checks.h
index 243a1ef..075e902 100644
--- a/include/types/checks.h
+++ b/include/types/checks.h
@@ -18,7 +18,7 @@
 
 #include <import/ist.h>
 #include <haproxy/list-t.h>
-#include <common/regex.h>
+#include <haproxy/regex-t.h>
 #include <haproxy/buf-t.h>
 
 #include <types/connection.h>