refactor: try to refactor the load config code to 2 clear pathes

[qs-wang]

• split loadConfigByProvider to a separate method to make if/else statement clearer
• split loadPrivateConfigFromFile to a separate method for reuse in if/else branches

I tried to make some changes for my own purpose. While I read the code although the code works perfectly, it a little bit hard to understand and change because the config loading logic from the provider and file are mixed. I refactored it to split the loading logic , i.e. loading from provider and file, to 2 methods, which made my changes easier. Later on I found other solution so the changes got dropped, but I am trying to push the refactor to see if anyone is interested.

If your build fails due to your commit message not passing the build checks, please review the guidelines here: https://github.com/edgexfoundry/go-mod-bootstrap/blob/main/.github/Contributing.md

PR Checklist

Please check if your PR fulfills the following requirements:

• [y] I am not introducing a breaking change (if you are, flag in conventional commit message with BREAKING CHANGE: describing the break)
• [y] I am not introducing a new dependency (add notes below if you are)
• [n] I have added unit tests for the new feature or bug fix (if not, why?) refactoring the code, should not change any logic, passed all existing test
• [y] I have fully tested (add details below) this the new feature or bug fix (if not, why?)
• [n] I have opened a PR for the related docs change (if not, why?) refactoring code, no doc change is needed

Testing Instructions

New Dependency Instructions (If applicable)

[jackchenjc]

Hi @qs-wang,

Thanks for the refactoring. I've left a comment below about a minor detail I noticed.

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

Attention: Patch coverage is 0% with 78 lines in your changes missing coverage. Please review.

Project coverage is 46.20%. Comparing base (53b414d) to head (f4834ce).

Files with missing lines	Patch %	Lines
bootstrap/config/config.go	0.00%	78 Missing ⚠️

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #814      +/-   ##
==========================================
- Coverage   46.51%   46.20%   -0.31%     
==========================================
  Files          62       62              
  Lines        3603     3627      +24     
==========================================
  Hits         1676     1676              
- Misses       1805     1829      +24     
  Partials      122      122              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.