S2S DNS discovery fix

[jacekwegr]

This PR fixes an issue with S2S connections using DNS discovery where connecting to another server would fail. The root cause was that inet_res:getbyname/3 returns a DNS type instead of the expected inet type needed for establishing connection. The updated logic now includes a proper lookup for the correct inet type to ensure successful connections.

Previously, the Erlang documentation did not clearly specify this behavior, which could be misleading. More details can be found here: erlang/otp#5803.

Testing was performed by mocking the appropriate inet functions. An alternative solution could involve setting up a local DNS server or using external tools like dnsmasq to set up a lightweight DNS resolver. However, this would require installing additional dependencies in the CI environment, so mocking was chosen as a simpler solution.

[codecov]

Codecov Report

Attention: Patch coverage is 92.30769% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 84.46%. Comparing base (e0b6504) to head (edf9530).
Report is 25 commits behind head on master.

Files	Patch %	Lines
src/ejabberd_s2s_out.erl	92.30%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4278      +/-   ##
==========================================
+ Coverage   84.42%   84.46%   +0.04%     
==========================================
  Files         553      553              
  Lines       33582    33591       +9     
==========================================
+ Hits        28352    28374      +22     
+ Misses       5230     5217      -13     

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[mongoose-im]

elasticsearch_and_cassandra_26 / elasticsearch_and_cassandra_mnesia / edf9530
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small_tests_26_arm64 / small_tests / edf9530
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ldap_mnesia_25 / ldap_mnesia / edf9530
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dynamic_domains_mysql_redis_26 / mysql_redis / edf9530
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dynamic_domains_pgsql_mnesia_25 / pgsql_mnesia / edf9530
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ldap_mnesia_26 / ldap_mnesia / edf9530
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dynamic_domains_mssql_mnesia_26 / odbc_mssql_mnesia / edf9530
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dynamic_domains_pgsql_mnesia_26 / pgsql_mnesia / edf9530
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internal_mnesia_26 / internal_mnesia / edf9530
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pgsql_mnesia_25 / pgsql_mnesia / edf9530
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mysql_redis_26 / mysql_redis / edf9530
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mssql_mnesia_26 / odbc_mssql_mnesia / edf9530
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pgsql_mnesia_26 / pgsql_mnesia / edf9530
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OK: 4934 / Failed: 0 / User-skipped: 118 / Auto-skipped: 0

[NelsonVides]

Excellent, thank you so much for fixing this!