adding multitenancy support for mod_carboncopy

[DenysGonchar]

This PR introduces dynamic domains support for mod_carboncopy.
Service discovery doesn't work for dynamic domains (as mod_disco doesn't support it yet), but still works correctly for statically configured domains

for a local testing you can use this command:

test-runner.sh --skip-small-tests --skip-cover --spec dynamic_domains.spec --preset pgsql_mnesia -- carboncopy
test-runner.sh --skip-small-tests --skip-cover --preset pgsql_mnesia -- carboncopy

[codecov]

Codecov Report

Merging #3130 (ab2a243) into master (45a47ec) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3130      +/-   ##
==========================================
+ Coverage   79.44%   79.47%   +0.03%     
==========================================
  Files         395      395              
  Lines       32167    32168       +1     
==========================================
+ Hits        25555    25567      +12     
+ Misses       6612     6601      -11     

Impacted Files	Coverage Δ
src/ejabberd_app.erl	93.75% <ø> (ø)
src/mod_carboncopy.erl	88.81% <100.00%> (+0.07%)	⬆️
src/ejabberd_c2s.erl	89.35% <0.00%> (+0.22%)	⬆️
src/mod_roster.erl	76.85% <0.00%> (+0.23%)	⬆️
src/ejabberd_sm.erl	84.51% <0.00%> (+0.67%)	⬆️
src/mod_bosh_socket.erl	78.88% <0.00%> (+1.24%)	⬆️
...bal_distrib/mod_global_distrib_hosts_refresher.erl	73.58% <0.00%> (+1.88%)	⬆️

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[NelsonVides]

Neat, and very good insight on how to carry the work for the multitenancy migration, thanks!

[NelsonVides]

Brilliant, thanks for the idea!