Change big test directory structure

[kanes115]

No description provided.

[kanes115]

TODO:

• Check CI compatibility
• Adjust docs
• Ensure scripts in tools/ folder are adjusted properly

[codecov-io]

Codecov Report

Merging #1778 into master will increase coverage by 4.97%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1778      +/-   ##
==========================================
+ Coverage   69.46%   74.44%   +4.97%     
==========================================
  Files         290      290              
  Lines       26931    26931              
==========================================
+ Hits        18707    20048    +1341     
+ Misses       8224     6883    -1341

Impacted Files	Coverage Δ
src/node_flat.erl	73.99% <0%> (-0.31%)	⬇️
src/mod_muc.erl	72.62% <0%> (-0.28%)	⬇️
src/mod_pubsub.erl	66.01% <0%> (-0.19%)	⬇️
src/mod_mam_utils.erl	87.41% <0%> (+0.68%)	⬆️
src/mod_bosh_socket.erl	81.66% <0%> (+1%)	⬆️
src/ejabberd_config.erl	63.99% <0%> (+1.08%)	⬆️
src/rdbms/mongoose_rdbms.erl	71.22% <0%> (+1.43%)	⬆️
src/mod_bosh.erl	94.95% <0%> (+1.68%)	⬆️
...bal_distrib/mod_global_distrib_hosts_refresher.erl	86.66% <0%> (+2.22%)	⬆️
src/cyrsasl.erl	85% <0%> (+2.5%)	⬆️
... and 14 more

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