SCB-850 Support discover instances from kubernetes cluster

[little-cui]

Follow this checklist to help us incorporate your contribution quickly and easily:

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[little-cui]

#394

[codecov-io]

Codecov Report

Merging #433 into master will decrease coverage by 0.02%.
The diff coverage is 70.01%.

@@            Coverage Diff             @@
##           master     #433      +/-   ##
==========================================
- Coverage   69.29%   69.27%   -0.03%     
==========================================
  Files         140      145       +5     
  Lines       10826    11023     +197     
==========================================
+ Hits         7502     7636     +134     
+ Misses       2845     2814      -31     
- Partials      479      573      +94

Impacted Files	Coverage Δ
pkg/log/zap.go	86.91% <ø> (ø)	⬆️
server/infra/discovery/cache_kv.go	95.6% <ø> (ø)
pkg/log/log_go19.go	100% <ø> (ø)	⬆️
...ver/plugin/infra/discovery/etcd/listwatch_inner.go	100% <ø> (ø)
server/plugin/plugin.go	75% <0%> (-1.42%)	⬇️
server/core/core.go	0% <0%> (ø)	⬆️
server/core/config.go	0% <0%> (ø)	⬆️
server/core/microservice.go	71.23% <0%> (-4.77%)	⬇️
server/plugin/infra/quota/buildin/common.go	22.85% <0%> (ø)	⬆️
pkg/gopool/goroutines.go	100% <100%> (ø)	⬆️
... and 63 more

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[coveralls]

Coverage increased (+0.4%) to 72.489% when pulling 4f0e314 on little-cui:master into 7f97881 on apache:master.

[tianxiaoliang]

ok

[asifdxtreme]

@little-cui please update the License files for release

[asifdxtreme]

Need to update the License file for new dependencies added

[little-cui]

Hi, all. I have finish this issue now, you can view the integration/k8s/README.md for more details