[metrics] Do not create the registry when users disable metrics in the option

[jolestar]

1. Do not create the registry when users disable metrics in the option.
2. Unify metrics name, use xxx_total for Counter metrics.

[codecov]

Codecov Report

Merging #2979 (d19044a) into master (e26f2ce) will increase coverage by 0.24%.
The diff coverage is 29.36%.

@@            Coverage Diff             @@
##           master    #2979      +/-   ##
==========================================
+ Coverage   33.23%   33.46%   +0.24%     
==========================================
  Files         517      515       -2     
  Lines       45435    45662     +227     
  Branches    20694    20812     +118     
==========================================
+ Hits        15094    15278     +184     
+ Misses      16140    16109      -31     
- Partials    14201    14275      +74     

Flag	Coverage Δ
unittests	33.46% <29.36%> (+0.24%)	⬆️

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

Impacted Files	Coverage Δ
account/src/account_storage.rs	50.50% <0.00%> (-1.76%)	⬇️
block-relayer/src/block_relayer.rs	25.67% <0.00%> (+0.54%)	⬆️
chain/api/src/errors.rs	25.00% <0.00%> (-6.81%)	⬇️
cmd/generator/src/lib.rs	100.00% <ø> (ø)
commons/metrics/src/metric_server.rs	0.00% <0.00%> (ø)
config/src/metrics_config.rs	53.93% <0.00%> (-2.11%)	⬇️
config/src/rpc_config.rs	46.62% <0.00%> (-1.19%)	⬇️
...ntrib-contracts/src/eth_state_verifier_test/mod.rs	30.34% <0.00%> (-0.69%)	⬇️
contrib-contracts/src/genesis_nft_test.rs	35.30% <0.00%> (+1.97%)	⬆️
contrib-contracts/src/merkle_distributor_test.rs	22.56% <0.00%> (+1.19%)	⬆️
... and 187 more

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