Add host.name to process metrics

[mariomac]

One of the many host attributes that we should add: https://opentelemetry.io/docs/specs/semconv/resource/process/

To be fully compliant with OTEL, In a future PR I'll move the host name and other metadata (process info, k8s metadata) to the resource-level attributes or the target_info metric.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.65%. Comparing base (512e9d0) to head (7649ec4).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #973      +/-   ##
==========================================
+ Coverage   80.56%   80.65%   +0.08%     
==========================================
  Files         134      134              
  Lines       10591    10601      +10     
==========================================
+ Hits         8533     8550      +17     
+ Misses       1557     1552       -5     
+ Partials      501      499       -2     

Flag	Coverage Δ
integration-test	55.80% <90.90%> (+0.07%)	⬆️
k8s-integration-test	59.15% <100.00%> (+0.16%)	⬆️
oats-test	36.07% <54.54%> (-0.01%)	⬇️
unittests	50.60% <100.00%> (+0.01%)	⬆️

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