feat(metaserver): add node cpu usage ratio metric

[cheney-lin]

What type of PR is this?

Enhancements

What this PR does / why we need it:

Which issue(s) this PR fixes:

Special notes for your reviewer:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (bf2d03c) 53.26% compared to head (bc45178) 53.36%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #339      +/-   ##
==========================================
+ Coverage   53.26%   53.36%   +0.10%     
==========================================
  Files         431      431              
  Lines       47320    47368      +48     
==========================================
+ Hits        25204    25280      +76     
+ Misses      19261    19238      -23     
+ Partials     2855     2850       -5     

Flag	Coverage Δ
unittest	53.36% <100.00%> (+0.10%)	⬆️

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Files	Coverage Δ
pkg/metaserver/agent/metric/malachite/fetcher.go	53.09% <100.00%> (+0.11%)	⬆️

... and 17 files with indirect coverage changes

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