RESOLV: supress deprecation warnings

In theory new API might be somewhat better.

But:

1) it's fairly new: `ares_search_dnsrec()` and `ares_query_dnsrec()`
were introduced in c-ares-1.28 while even CentOS Stream 10 has
c-ares-1.25, so SSSD would need to support (fallback) old API anyway.

2) SSSD doesn't make heavy use of DNS, so potential performance
improvements are really negligible.

On the other hand, old API/ABI will be available for a long time:
c-ares/c-ares#732 (comment)

For those reasons it's not worth the effort to port code to new API
right now.

src/resolv/async_resolv.c

@@ -27,7 +27,6 @@
 #include <arpa/inet.h>
 #include <arpa/nameser.h>
 
-#include <ares.h>
 #include <talloc.h>
 #include <tevent.h>
 

src/resolv/async_resolv.h

@@ -27,6 +27,7 @@
 #define __ASYNC_RESOLV_H__
 
 #include <netdb.h>
+#define CARES_NO_DEPRECATED
 #include <ares.h>
 
 #include "config.h"