feat: Add metrics module

[diwufeiwen]

resolve filecoin-project/venus#5054

[codecov-commenter]

Codecov Report

Merging #220 (6c005ae) into master (2bf3c58) will decrease coverage by 0.35%.
The diff coverage is 1.88%.

@@            Coverage Diff             @@
##           master     #220      +/-   ##
==========================================
- Coverage   15.47%   15.12%   -0.36%     
==========================================
  Files          56       57       +1     
  Lines        5403     5502      +99     
==========================================
- Hits          836      832       -4     
- Misses       4488     4591     +103     
  Partials       79       79              

Flag	Coverage Δ
unittests	15.12% <1.88%> (-0.36%)	⬇️

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Impacted Files	Coverage Δ
main.go	0.00% <0.00%> (ø)
metrics/exporter.go	0.00% <0.00%> (ø)
models/sqlite/shared_params.go	58.82% <ø> (ø)
service/address_service.go	0.00% <ø> (ø)
service/message_service.go	0.00% <0.00%> (ø)
service/message_state_refresh.go	0.00% <0.00%> (ø)
config/config.go	100.00% <100.00%> (ø)