DNS Client API

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                   THIS API IS STILL WORK IN PROGRESS
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The DNS Client API for Zephyr is a collection of C files:

    - dns_pack.h, dns_pack.c:
        RFC 1035 serialization and deserialization functions

    - dns_utils.h. dns_utils.c:
	Helper functions

TODO

    - Implement high-level functions to handle the server's response
    - Remove:
        * dns_query in src/main.c and handle the Transaction
          Identifier internally.
        * dns_response in src/main.c once high-level functions are
          available.