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/src/http_htx.c b/src/http_htx.c
index d5d8747..e3e21d7 100644
--- a/src/http_htx.c
+++ b/src/http_htx.c
@@ -20,7 +20,7 @@
 #include <haproxy/regex.h>
 #include <haproxy/sample.h>
 
-#include <common/cfgparse.h>
+#include <haproxy/cfgparse.h>
 #include <haproxy/h1.h>
 #include <haproxy/http.h>
 #include <haproxy/http_htx.h>