refactor(SPV-1071): cleanup in config package.

[dorzepowski]

Pull Request Checklist

• 📖 I created my PR using provided : CODE_STANDARDS
• 📖 I have read the short Code of Conduct: CODE_OF_CONDUCT
• 🏠 I tested my changes locally.
• ✅ I have provided tests for my changes.
• 📝 I have used conventional commits.
• 📗 I have updated any related documentation.
• 💾 PR was issued based on the Github or Jira issue.

[github-actions]

Manual Tests

💚 Manual testing by @chris-4chain resulted in success.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 26.55367% with 260 lines in your changes missing coverage. Please review.

Project coverage is 45.85%. Comparing base (62ba56c) to head (436661e).

Files with missing lines	Patch %	Lines
config/config_to_options.go	0.00%	181 Missing ⚠️
cmd/main.go	0.00%	26 Missing ⚠️
server/server.go	10.52%	17 Missing ⚠️
logging/logging.go	0.00%	11 Missing ⚠️
config/check_block_header_service.go	0.00%	5 Missing ⚠️
config/load_config.go	64.28%	2 Missing and 3 partials ⚠️
config/validate_arc.go	87.87%	2 Missing and 2 partials ⚠️
engine/logging/adapters.go	20.00%	4 Missing ⚠️
config/config.go	0.00%	2 Missing ⚠️
engine/client.go	0.00%	1 Missing and 1 partial ⚠️
... and 2 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #722      +/-   ##
==========================================
- Coverage   46.37%   45.85%   -0.52%     
==========================================
  Files         314      314              
  Lines       13049    13047       -2     
==========================================
- Hits         6051     5983      -68     
- Misses       6417     6508      +91     
+ Partials      581      556      -25     

Flag	Coverage Δ
unittests	45.85% <26.55%> (-0.52%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
config/defaults.go	100.00% <100.00%> (ø)
config/validate_app_config.go	100.00% <100.00%> (ø)
logging/gin_loggers.go	63.41% <100.00%> (ø)
server/middleware/appcontext_middleware.go	100.00% <100.00%> (ø)
tests/tests.go	100.00% <100.00%> (+12.00%)	⬆️
config/flags.go	42.10% <75.00%> (ø)
config/config.go	50.00% <0.00%> (-50.00%)	⬇️
engine/client.go	55.73% <0.00%> (-0.93%)	⬇️
engine/tester/logger.go	0.00% <0.00%> (ø)
config/validate_arc.go	87.87% <87.87%> (ø)
... and 7 more

... and 4 files with indirect coverage changes

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