Introduce MergeFrom for profiles

[iblancasa]

This is part of #13106
It introduces a new MergeFrom method, which allows merging to profiles.

[codecov]

Codecov Report

❌ Patch coverage is 76.75545% with 96 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.43%. Comparing base (2e19689) to head (dc44db8).
⚠️ Report is 104 commits behind head on main.

Files with missing lines	Patch %	Lines
pdata/pprofile/merge.go	76.75%	64 Missing and 32 partials ⚠️

❌ Your patch status has failed because the patch coverage (76.75%) 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   #13588      +/-   ##
==========================================
- Coverage   91.57%   91.43%   -0.15%     
==========================================
  Files         639      640       +1     
  Lines       42153    42566     +413     
==========================================
+ Hits        38603    38920     +317     
- Misses       2719     2783      +64     
- Partials      831      863      +32     

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[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 14 days.

[dmathieu]

Couldn't the logic be simplified by using the Set* methods introduced earlier? (that's the reason they were introduced)

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 14 days.

[github-actions]

Closed as inactive. Feel free to reopen if this PR is still being worked on.