[service]: add new subcommand to examine the initial configuration

[VihasMakwana]

Description

Why is this useful?

• Users might want to examine the config if they face any errors at boot time. This subcommand prints the configuration on stdout after merging and resolving from all the --config sources.
• The command prints the configuration even if it's invalid. This can help user to track down the faulty piece of config.

Usage

./otelcorecol examine --config=file:file.yaml --config=http://remote:8080/config --config=file:file2.yaml

Link to tracking issue

Fixes ##11479

Testing

Added unit test cases.

Documentation

Updated readme.

[codecov]

Codecov Report

Attention: Patch coverage is 90.32258% with 3 lines in your changes missing coverage. Please review.

Project coverage is 92.18%. Comparing base (56fbf4c) to head (9116f55).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
otelcol/command_print.go	90.00%	2 Missing and 1 partial ⚠️

❌ Your patch status has failed because the patch coverage (90.32%) is below the target coverage (95.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11775      +/-   ##
==========================================
- Coverage   92.18%   92.18%   -0.01%     
==========================================
  Files         465      466       +1     
  Lines       25275    25306      +31     
==========================================
+ Hits        23301    23329      +28     
- Misses       1575     1577       +2     
- Partials      399      400       +1     

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[VihasMakwana]

@dmitryax @mauri870 can you take a look?

[mauri870]

Can you change to fmt.Printf here? This output is likely to be piped/redirected and I would rather not have a random timestamp at the start of the output.

[mauri870]

Reviewed again, LGTM. Thanks for adding a test to check the tool output.

[mx-psi]

cc @open-telemetry/collector-approvers This PR adds a new experimental (under a feature gate) subcommand to examine the initial configuration. I will merge this PR in one week if there are no further comments

[evan-bradley]

Thanks @VihasMakwana! This looks good, I mostly have copyediting notes. The most important one is that we should describe how to use this in the changelog.

[evan-bradley]

@VihasMakwana it looks like you have a few failing checks and tests, could you take a look at those?

[evan-bradley]

@VihasMakwana Sorry for the churn, needs a make gotidy now.

[mx-psi]

@VihasMakwana I will merge this after you have fixed the merge conflicts!

[VihasMakwana]

@mx-psi I've rebased main. Once CI is good, this can be merged.