Rework on metrics storage

[jolestar]

重构了 miner 和 rpc 相关的 metrics。

storage 的 metric 在下一个 pr。

[codecov]

Codecov Report

Merging #2973 (ea86ddc) into master (ed8bf2d) will decrease coverage by 0.03%.
The diff coverage is 40.33%.

@@            Coverage Diff             @@
##           master    #2973      +/-   ##
==========================================
- Coverage   33.20%   33.17%   -0.02%     
==========================================
  Files         516      517       +1     
  Lines       45294    45437     +143     
  Branches    20639    20695      +56     
==========================================
+ Hits        15036    15070      +34     
- Misses      15932    16013      +81     
- Partials    14326    14354      +28     

Flag	Coverage Δ
unittests	33.17% <40.33%> (-0.02%)	⬇️

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

Impacted Files	Coverage Δ
commons/metrics/src/lib.rs	14.52% <0.00%> (ø)
...reate_block_template/test_create_block_template.rs	20.90% <0.00%> (+2.52%)	⬆️
rpc/server/src/module/node_rpc.rs	18.92% <0.00%> (-1.08%)	⬇️
miner/src/lib.rs	34.65% <20.00%> (-0.03%)	⬇️
rpc/middleware/src/tests.rs	20.84% <25.00%> (-1.89%)	⬇️
rpc/middleware/src/lib.rs	44.45% <26.32%> (-1.93%)	⬇️
rpc/server/src/api_registry.rs	38.71% <33.34%> (-11.29%)	⬇️
rpc/server/src/service.rs	38.07% <33.34%> (+0.16%)	⬆️
miner/src/metrics.rs	55.56% <45.46%> (+13.46%)	⬆️
miner/src/task.rs	40.91% <60.00%> (+5.91%)	⬆️
... and 94 more

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