refactor(core): clean up define metric and add missing functionality

[kptkin]

Description

• Fixes WB-NNNNN
• Fixes #NNNN

What does the PR do? Include a concise description of the PR contents.

• I updated CHANGELOG.md, or it's not applicable

Testing

How was this PR tested?

[codecov]

Codecov Report

Attention: Patch coverage is 67.05202% with 57 lines in your changes are missing coverage. Please review.

Project coverage is 72.64%. Comparing base (e95426d) to head (93bdcd5).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7447      +/-   ##
==========================================
- Coverage   74.91%   72.64%   -2.28%     
==========================================
  Files         519      521       +2     
  Lines       54631    56177    +1546     
==========================================
- Hits        40928    40808     -120     
- Misses      13302    14972    +1670     
+ Partials      401      397       -4     

Flag	Coverage Δ
func	43.35% <48.57%> (+0.07%)	⬆️
system	61.20% <82.14%> (-1.72%)	⬇️
unit	54.39% <20.23%> (-0.91%)	⬇️

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Files	Coverage Δ
core/pkg/server/sender.go	63.08% <100.00%> (-9.75%)	⬇️
core/pkg/server/stream.go	96.58% <100.00%> (-1.34%)	⬇️
core/internal/runmetric/runmetric.go	50.00% <50.00%> (ø)
core/internal/runmetric/runmetric_sender.go	66.66% <66.66%> (ø)
core/pkg/server/handler.go	68.09% <58.13%> (-5.69%)	⬇️
core/internal/runmetric/runmetric_handler.go	65.62% <65.62%> (ø)

... and 100 files with indirect coverage changes