feat: add metric instrumentation

[Tochemey]

#170

[codecov]

Codecov Report

Attention: 72 lines in your changes are missing coverage. Please review.

Comparison is base (f862fff) 90.18% compared to head (883c728) 88.97%.

❗ Current head 883c728 differs from pull request most recent head 8b7f606. Consider uploading reports for the commit 8b7f606 to get more accurate results

Files	Patch %	Lines
actors/pid.go	35.55%	26 Missing and 3 partials ⚠️
actors/actor_system.go	24.13%	20 Missing and 2 partials ⚠️
metric/actor_metric.go	68.08%	10 Missing and 5 partials ⚠️
metric/system_metric.go	72.72%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #196      +/-   ##
==========================================
- Coverage   90.18%   88.97%   -1.21%     
==========================================
  Files          42       44       +2     
  Lines        4667     4809     +142     
==========================================
+ Hits         4209     4279      +70     
- Misses        368      428      +60     
- Partials       90      102      +12     

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