[confmap] - New merging mode to combine components

[VihasMakwana]

Koanf's default merging strategy currently overrides static values such as slices, numbers, and strings. However, lists of components should be treated as a special case. This pull request introduces a new feature gate to allow for merging lists instead of discarding the existing ones.

With this new merging strategy:

• Lists under the service configuration are merged rather than replaced.
• The merging logic is name-aware, meaning that if components with the same name appear in both lists, they will only appear once in the final merged list.
• This strategy only affects configurations under service::*.

Link to tracking issue

Related issues:

• Append components flag #8754
• Allow instantiating extensions in separate configs #8394
• [ConfMap] - Providing custom merge method for koanf's Map.Merge #10370

Testing

• Added

Documentation

• To be added

Note: I’d appreciate your feedback on this 🙏

[codecov]

Codecov Report

Attention: Patch coverage is 84.78261% with 7 lines in your changes missing coverage. Please review.

Project coverage is 92.18%. Comparing base (e99074d) to head (51d2a56).

Files with missing lines	Patch %	Lines
confmap/merge.go	82.50%	5 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11046      +/-   ##
==========================================
- Coverage   92.20%   92.18%   -0.02%     
==========================================
  Files         405      406       +1     
  Lines       19244    19290      +46     
==========================================
+ Hits        17743    17782      +39     
- Misses       1134     1139       +5     
- Partials      367      369       +2     

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[VihasMakwana]

@codeboten @open-telemetry/collector-approvers I would appreciate any feedback you guys might have!

[mx-psi]

I think we need to discuss more on #8754 before moving forward with any concrete solution

[VihasMakwana]

I think we need to discuss more on #8754 before moving forward with any concrete solution

Sure. Let's discuss more on #8754.

I'll move this PR to draft then.