REORG: include: move cfgparse.h to haproxy/cfgparse.h

There's no point splitting the file in two since only cfgparse uses the
types defined there. A few call places were updated and cleaned up. All
of them were in C files which register keywords.

There is nothing left in common/ now so this directory must not be used
anymore.
diff --git a/contrib/prometheus-exporter/service-prometheus.c b/contrib/prometheus-exporter/service-prometheus.c
index bc968d9..9375f0a 100644
--- a/contrib/prometheus-exporter/service-prometheus.c
+++ b/contrib/prometheus-exporter/service-prometheus.c
@@ -17,7 +17,7 @@
 #include <haproxy/applet.h>
 #include <haproxy/backend.h>
 #include <haproxy/api.h>
-#include <common/cfgparse.h>
+#include <haproxy/cfgparse.h>
 #include <haproxy/frontend.h>
 #include <haproxy/global.h>
 #include <haproxy/http.h>