Add validate command to validate collector config

[codeboten]

This is bringing back the functionality initially submitted in @Chinwendu20's PR: #6445

Adds a validate method which validates the configuration

Link to tracking Issue: #4613

[jmacd]

🎉

[codecov]

Codecov Report

Patch coverage: 77.41% and project coverage change: +0.27 🎉

Comparison is base (897a316) 90.82% compared to head (8bccc7f) 91.09%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7835      +/-   ##
==========================================
+ Coverage   90.82%   91.09%   +0.27%     
==========================================
  Files         296      297       +1     
  Lines       14840    14831       -9     
==========================================
+ Hits        13478    13511      +33     
+ Misses       1087     1044      -43     
- Partials      275      276       +1     

Impacted Files	Coverage Δ
otelcol/command_validate.go	70.83% <70.83%> (ø)
otelcol/collector.go	78.72% <100.00%> (+0.94%)	⬆️
otelcol/command.go	82.14% <100.00%> (+0.66%)	⬆️

... and 3 files with indirect coverage changes

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[jpkrohling]

@Chinwendu20, would you like to review this one as well?

[Chinwendu20]

Thanks for continuing with the PR, looks good to me.