[dns-sd] DNS-SD server implementation (#6103)

This commit implements the DNS-SD server:
- Handle Standard DNS Query from clients
  - Supported resource records: PTR, SRV, TXT, AAAA
- Query services from SRP server
- Add tests
  - simulation test using DNS client (only test AAAA query)
  - OTBR test using dig command to verify all resource records can be
    queried successfully

script/check-size

@@ -115,6 +115,7 @@ size_nrf52840_version()
         "DIAGNOSTIC=1"
         "DISABLE_DOC=1"
         "DNS_CLIENT=1"
+        "DNSSD_SERVER=1"
         "ECDSA=1"
         "FULL_LOGS=1"
         "JAM_DETECTION=1"