Unify checks for chat markers

[NelsonVides]

Currently checking if a stanza contains a chat markers is triplicated in
three different modules. Implement all of it in mod_smart_markers and
make the other two places simply call this one.

[DenysGonchar]

thanks for moving it in a separate helper module

[codecov]

Codecov Report

Merging #3080 (f99a331) into master (fad3ff7) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3080      +/-   ##
==========================================
+ Coverage   78.82%   78.84%   +0.02%     
==========================================
  Files         379      380       +1     
  Lines       31234    31227       -7     
==========================================
+ Hits        24620    24622       +2     
+ Misses       6614     6605       -9     

Impacted Files	Coverage Δ
src/inbox/mod_inbox_utils.erl	92.85% <100.00%> (-0.39%)	⬇️
src/mam/mod_mam_utils.erl	89.56% <100.00%> (-0.14%)	⬇️
src/mod_smart_markers.erl	89.58% <100.00%> (+0.29%)	⬆️
src/mongoose_chat_markers.erl	100.00% <100.00%> (ø)
src/elasticsearch/mongoose_elasticsearch.erl	76.92% <0.00%> (-7.70%)	⬇️
src/mam/mod_mam_elasticsearch_arch.erl	86.60% <0.00%> (-1.79%)	⬇️
src/global_distrib/mod_global_distrib_utils.erl	65.09% <0.00%> (-0.95%)	⬇️
src/ejabberd_s2s_out.erl	57.89% <0.00%> (-0.23%)	⬇️
src/mod_muc_room.erl	77.50% <0.00%> (-0.06%)	⬇️
src/mod_muc_log.erl	77.72% <0.00%> (ø)
... and 8 more

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