feat: add monitoring for kafka message metadata

[Elia-Renzoni]

This PR introduces monitoring for Kafka message metadata to improve observability
and traceability of message processing.

Related Issue: #3491

[codecov]

Codecov Report

❌ Patch coverage is 0% with 30 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.41%. Comparing base (feab3a4) to head (71efd79).
⚠️ Report is 13 commits behind head on master.

Files with missing lines	Patch %	Lines
extensions/impl/kafka/source.go	0.00%	30 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3923      +/-   ##
==========================================
- Coverage   71.49%   71.41%   -0.07%     
==========================================
  Files         453      453              
  Lines       52084    52191     +107     
==========================================
+ Hits        37234    37272      +38     
- Misses      11948    12003      +55     
- Partials     2902     2916      +14     

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