config: support manage the component configuration

[rleungx]

What problem does this PR solve?

Provide a way to manage components' configuration in the cluster.

What is changed and how it works?

This PR is a basic implementation.

Check List

Tests

• Unit test

[codecov-io]

Codecov Report

Merging #1977 into master will decrease coverage by 0.9%.
The diff coverage is 55.83%.

@@            Coverage Diff            @@
##           master   #1977      +/-   ##
=========================================
- Coverage    77.7%   76.8%   -0.91%     
=========================================
  Files         179     181       +2     
  Lines       18407   19102     +695     
=========================================
+ Hits        14304   14671     +367     
- Misses       3022    3303     +281     
- Partials     1081    1128      +47

Impacted Files	Coverage Δ
server/cluster/cluster.go	80.39% <100%> (+0.02%)	⬆️
client/metrics.go	100% <100%> (ø)	⬆️
pkg/typeutil/duration.go	78.94% <100%> (+2.47%)	⬆️
server/grpc_service.go	50.92% <13.92%> (-6.32%)	⬇️
client/config_client.go	43.86% <43.86%> (ø)
server/server.go	75.23% <46.82%> (-8.26%)	⬇️
server/core/storage.go	73.07% <60%> (-2.38%)	⬇️
server/config/config.go	82.05% <66.66%> (ø)	⬆️
server/config/component_config.go	80.14% <80.14%> (ø)
server/kv/etcd_kv.go	72.72% <0%> (-11.69%)	⬇️
... and 12 more

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