Feature/gsvc interface

[gqcn]

1. Change struct implements gsvc.Service to interface gsvc.Service.
2. Update contribution packages contrib/registry/etcd and contrib/registry/polaris for this change accordingly.

[codecov-commenter]

Codecov Report

Merging #1871 (84d7972) into develop (6d0b4fa) will decrease coverage by 0.22%.
The diff coverage is 59.09%.

@@             Coverage Diff             @@
##           develop    #1871      +/-   ##
===========================================
- Coverage    73.46%   73.23%   -0.23%     
===========================================
  Files          494      506      +12     
  Lines        44175    45440    +1265     
===========================================
+ Hits         32451    33276     +825     
- Misses        9770    10142     +372     
- Partials      1954     2022      +68     

Flag	Coverage Δ
go-1.15	?
go-1.15-386	73.17% <59.09%> (?)
go-1.16	?
go-1.16-amd64	73.16% <59.09%> (?)
go-1.17	?
go-1.17-386	73.22% <59.09%> (?)
go-1.17-amd64	73.18% <59.09%> (?)

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

Impacted Files	Coverage Δ
contrib/drivers/mssql/mssql.go	85.83% <ø> (ø)
contrib/drivers/mysql/mysql.go	64.34% <ø> (ø)
contrib/drivers/pgsql/pgsql.go	11.11% <0.00%> (ø)
database/gdb/gdb.go	65.81% <ø> (+1.53%)	⬆️
encoding/gjson/gjson.go	84.01% <ø> (ø)
net/gclient/gclient_config.go	39.13% <0.00%> (ø)
net/gclient/gclient_response.go	72.22% <0.00%> (-3.46%)	⬇️
net/gclient/gclient_tracing.go	44.00% <ø> (ø)
net/gclient/gclient_tracing_tracer.go	0.00% <ø> (ø)
net/ghttp/ghttp.go	100.00% <ø> (ø)
... and 67 more

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