Add the DNS query hook to net context

This change
 - adds a query hook to android_net_context
 - exposes relevant definitions to netd
 - corrects a bug in query hooks' interaction with the cache

This change does not introduce any code to read the query hook
from the net context or make use of it.

Bug: 34953048
Test: Netd test suite passes
Change-Id: Ie091980e22ce9da07a3c4d387b371e544379d762
diff --git a/libc/dns/include/resolv_params.h b/libc/dns/include/resolv_params.h
index 49ae691..1b9d433 100644
--- a/libc/dns/include/resolv_params.h
+++ b/libc/dns/include/resolv_params.h
@@ -43,4 +43,15 @@
     uint8_t max_samples; // max # samples taken into account for statistics
 };
 
+typedef enum { res_goahead, res_nextns, res_modified, res_done, res_error }
+	res_sendhookact;
+
+typedef res_sendhookact (*res_send_qhook)(struct sockaddr * const *,
+					      const u_char **, int *,
+					      u_char *, int, int *);
+
+typedef res_sendhookact (*res_send_rhook)(const struct sockaddr *,
+					      const u_char *, int, u_char *,
+					      int, int *);
+
 #endif // _RESOLV_PARAMS_H