[metrics] Rework on sync metrics and peer score metrics

[jolestar]

1. disable metrics 的时候，不再记录 metrics。
2. 整理 sync 和 peer score 的 metrics。

其他模块逐步重构 #1738

[codecov]

Codecov Report

Merging #2957 (938d6f3) into master (4104430) will decrease coverage by 0.38%.
The diff coverage is 35.64%.

@@            Coverage Diff             @@
##           master    #2957      +/-   ##
==========================================
- Coverage   33.45%   33.08%   -0.37%     
==========================================
  Files         517      516       -1     
  Lines       45123    45128       +5     
  Branches    20576    20535      -41     
==========================================
- Hits        15093    14925     -168     
- Misses      15846    15975     +129     
- Partials    14184    14228      +44     

Flag	Coverage Δ
unittests	33.08% <35.64%> (-0.37%)	⬇️

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

Impacted Files	Coverage Δ
block-relayer/src/block_relayer.rs	23.13% <0.00%> (ø)
network/api/src/tests.rs	25.00% <0.00%> (ø)
node/src/node.rs	9.53% <0.00%> (-0.47%)	⬇️
sync/src/announcement/mod.rs	18.19% <0.00%> (ø)
sync/src/tasks/block_sync_task.rs	38.92% <ø> (+0.42%)	⬆️
sync/src/tasks/mock.rs	47.23% <0.00%> (ø)
sync/src/tasks/mod.rs	26.24% <0.00%> (-0.39%)	⬇️
sync/src/tasks/tests.rs	17.00% <0.00%> (+1.42%)	⬆️
sync/src/txn_sync/mod.rs	13.64% <0.00%> (ø)
sync/src/sync_metrics.rs	19.05% <16.67%> (-3.80%)	⬇️
... and 89 more

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