enhancement(kcmas): emit metric latency

[zzzzhhb]

What type of PR is this?

enhancements

What this PR does / why we need it:

add metric to monitor the metric data latency

Which issue(s) this PR fixes:

Special notes for your reviewer:

[codecov]

Codecov Report

Attention: 55 lines in your changes are missing coverage. Please review.

Comparison is base (35c0eb0) 53.39% compared to head (5458d41) 53.28%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #315      +/-   ##
==========================================
- Coverage   53.39%   53.28%   -0.12%     
==========================================
  Files         401      401              
  Lines       43913    43948      +35     
==========================================
- Hits        23448    23418      -30     
- Misses      17878    17953      +75     
+ Partials     2587     2577      -10     

Flag	Coverage Δ
unittest	53.28% <58.64%> (-0.12%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
cmd/base/context_fake.go	71.52% <100.00%> (+4.16%)	⬆️
cmd/base/options/auth.go	71.42% <100.00%> (+9.89%)	⬆️
pkg/custom-metric/provider/provider.go	82.54% <100.00%> (+2.12%)	⬆️
...kg/util/credential/authorization/authorizations.go	80.64% <100.00%> (ø)
pkg/util/credential/authorization/insecure.go	100.00% <100.00%> (ø)
pkg/util/credential/credentials.go	70.00% <100.00%> (ø)
pkg/util/credential/insecure.go	84.61% <100.00%> (ø)
pkg/util/credential/authorization/static.go	28.57% <0.00%> (ø)
pkg/custom-metric/store/local/local_store.go	67.67% <0.00%> (-0.35%)	⬇️
pkg/util/credential/authorization/dynamic.go	92.00% <92.00%> (ø)
... and 4 more

... and 10 files with indirect coverage changes

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