Syncer stats support timestamp

[absolute8511]

No description provided.

[codecov]

Codecov Report

Merging #50 into master will decrease coverage by 0.11%.
The diff coverage is 10.37%.

@@            Coverage Diff             @@
##           master      #50      +/-   ##
==========================================
- Coverage   44.57%   44.45%   -0.12%     
==========================================
  Files         149      149              
  Lines       21860    21922      +62     
==========================================
+ Hits         9744     9746       +2     
- Misses      10504    10566      +62     
+ Partials     1612     1610       -2

Impacted Files	Coverage Δ
common/stats.go	0% <ø> (ø)	⬆️
server/httpapi.go	15.27% <0%> (-0.35%)	⬇️
node/syncer_learner.go	0% <0%> (ø)	⬆️
server/server.go	57.26% <0%> (-0.51%)	⬇️
node/namespace.go	30.59% <0%> (-1.24%)	⬇️
node/remote_sync_mgr.go	1.88% <0%> (-0.09%)	⬇️
node/log_sender.go	0% <0%> (ø)	⬆️
rockredis/rockredis.go	35.35% <100%> (+0.09%)	⬆️
pkg/idutil/id.go	100% <100%> (ø)	⬆️
server/grpc_api.go	57.54% <100%> (+0.4%)	⬆️
... and 2 more

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