Do not post-process config when starting modules

[chrzaszcz]

Follow-up to #3469
The config should remain constant since it is stored in the persistent term.
This way it will be possible for modules to read config opts from the persistent term - this change will be done in the next PR.

We will most likely get rid of the unfolding altogether when converting all module options to maps.

[codecov]

Codecov Report

Merging #3488 (1603185) into module-config-map (4380fc6) will not change coverage.
The diff coverage is 100.00%.

@@                Coverage Diff                 @@
##           module-config-map    #3488   +/-   ##
==================================================
  Coverage              80.91%   80.91%           
==================================================
  Files                    416      416           
  Lines                  32352    32352           
==================================================
  Hits                   26179    26179           
  Misses                  6173     6173           

Impacted Files	Coverage Δ
src/config/mongoose_config_parser_toml.erl	97.81% <ø> (ø)
src/gen_mod.erl	67.46% <ø> (-0.26%)	⬇️
src/config/mongoose_config_parser.erl	64.70% <100.00%> (ø)
src/mongoose_modules.erl	100.00% <100.00%> (ø)
src/rdbms/mongoose_rdbms.erl	61.75% <0.00%> (-1.20%)	⬇️
src/domain/mongoose_domain_loader.erl	89.28% <0.00%> (-0.90%)	⬇️
src/pubsub/mod_pubsub.erl	73.19% <0.00%> (-0.12%)	⬇️
src/mod_muc_room.erl	77.09% <0.00%> (+0.11%)	⬆️
src/pubsub/mod_pubsub_db_mnesia.erl	92.85% <0.00%> (+0.42%)	⬆️
...c/global_distrib/mod_global_distrib_server_mgr.erl	77.40% <0.00%> (+0.56%)	⬆️
... and 2 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 4380fc6...1603185. Read the comment docs.