Add control flags in asynchronous DNS query API

#if __ANDROID_API__ >= 29

enum ResNsendFlags : uint32_t {

    // Send a single request to a single resolver and fail on timeout or network errors

    ANDROID_RESOLV_NO_RETRY = 1 << 0,

    // Do not cache the result of the lookup. The lookup may return a result that is already

    // in the cache, unless the ANDROID_RESOLV_NO_CACHE_LOOKUP flag is also specified.

    ANDROID_RESOLV_NO_CACHE_STORE = 1 << 1,

    // Don't lookup the request in cache, do not write back the response into the cache

    ANDROID_RESOLV_NO_CACHE_LOOKUP = 1 << 2,

};

/**

 * Look up the {|ns_class|, |ns_type|} Resource Record (RR) associated

 * with Domain Name |dname| on the given |network|.

 * The typical value for |ns_class| is ns_c_in, while |type| can be any

 * record type (for instance, ns_t_aaaa or ns_t_txt).

 * |flags| is a additional config to control actual querying behavior, see

 * ResNsendFlags for detail.

 *

 * Returns a file descriptor to watch for read events, or a negative

 * POSIX error code (see errno.h) if an immediate error occurs.

 */

int android_res_nquery(net_handle_t network,

        const char *dname, int ns_class, int ns_type) __INTRODUCED_IN(29);

        const char *dname, int ns_class, int ns_type,

        enum ResNsendFlags flags) __INTRODUCED_IN(29);

/**

 * Issue the query |msg| on the given |network|.

 * |flags| is a additional config to control actual querying behavior, see

 * ResNsendFlags for detail.

 *

 * Returns a file descriptor to watch for read events, or a negative

 * POSIX error code (see errno.h) if an immediate error occurs.

 */

int android_res_nsend(net_handle_t network,

        const uint8_t *msg, size_t msglen) __INTRODUCED_IN(29);

        const uint8_t *msg, size_t msglen, enum ResNsendFlags flags) __INTRODUCED_IN(29);

/**

 * Read a result for the query associated with the |fd| descriptor.