[refactor] Improved GetHTTPRoundTripper

[danish9039]

Which problem is this PR solving?

part of

• [Feature]: Elasticsearch support for API Keys #7225

Description of the changes

It is part of the planned work to add support for API authentication, as discussed in #7230 (comment)

1. Improved GetHTTPRoundTripper

   Previous Problems :

   • Auth Bypass: Secure TLS paths could bypass bearer token authentication.
   • Nil Return Risk: Could return a nil RoundTripper without error, causing panics.
   • Confusing TLS: Insecure mode with CAFile led to ambiguous TLS configuration.

   Refactored Solutions:

   • Consistent Auth: Always applies TLS first, then wraps with authentication.
   • Guaranteed Return: Ensures a valid, non-nil RoundTripper is always returned.
   • Clearer TLS: Streamlines TLS application for predictable behavior.

2. Refactored getConfigOptions

   • getESOptions: Extracted basic ES client options into a dedicated helper for modularity.
   • Health Check: Refined logic to disable health checks only when explicitly requested or when context-only bearer tokens are used, preventing startup issues.
   • HTTP Client: Integrated GetHTTPRoundTripper output directly into http.Client setup, ensuring full transport configuration from the start.

How was this change tested?

Checklist

• I have read https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md
• I have signed all commits
• I have added unit tests for the new functionality
• I have run lint and test steps successfully
  • for jaeger: make lint test
  • for jaeger-ui: npm run lint and npm run test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.27%. Comparing base (5b0b5a1) to head (8c9152d).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7313      +/-   ##
==========================================
+ Coverage   96.19%   96.27%   +0.08%     
==========================================
  Files         377      377              
  Lines       22898    22899       +1     
==========================================
+ Hits        22026    22046      +20     
+ Misses        657      645      -12     
+ Partials      215      208       -7     

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tailsampling-processor	0.48% <0.00%> (-0.01%)	⬇️
unittests	95.19% <100.00%> (+0.08%)	⬆️

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[yurishkuro]

Is this change purely a refactor or does it change the behavior? It seems to me that the TLS handling is different now. If so, please update the description/title to reflect what changed.

[danish9039]

Is this change purely a refactor or does it change the behavior? It seems to me that the TLS handling is different now. If so, please update the description/title to reflect what changed.

done