Add basic support for cluster flow control in Sentinel dashboard

[sczyh30]

Describe what this PR does / why we need it

Add basic support for cluster flow control in Sentinel dashboard

Does this pull request fix one issue?

Related to #200

Describe how you did it

• Update SentinelApiClient to support new-added command APIs
• Add controller for cluster config
• Add flow controller v2 for global rule pulling / pushing
• Extract dynamic rule provider and publisher interface for customized extensions
• Add basic cluster config service
• Add basic Nacos integration (in test as an example)
• Add frontend service and pages for Sentinel cluster flow control

Describe how to verify it

Run the dashboard.

Special notes for reviews

None.

[CarpenterLee]

LGTM

[codecov-io]

Codecov Report

Merging #302 into master will increase coverage by 0.49%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##             master    #302      +/-   ##
===========================================
+ Coverage     38.31%   38.8%   +0.49%     
- Complexity      932     941       +9     
===========================================
  Files           219     219              
  Lines          6921    6921              
  Branches        939     939              
===========================================
+ Hits           2652    2686      +34     
+ Misses         3937    3892      -45     
- Partials        332     343      +11

Impacted Files	Coverage Δ	Complexity Δ
...s/block/flow/controller/RateLimiterController.java	79.16% <0%> (-12.5%)	5% <0%> (-1%)
...a/com/alibaba/csp/sentinel/node/StatisticNode.java	67.21% <0%> (+1.63%)	22% <0%> (+1%)	⬆️
...a/csp/sentinel/slots/statistic/base/LongAdder.java	31.91% <0%> (+14.89%)	10% <0%> (+6%)	⬆️
...a/csp/sentinel/slots/statistic/base/Striped64.java	56.25% <0%> (+30.2%)	8% <0%> (+3%)	⬆️

---

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[codecov-io]

Codecov Report

Merging #302 into master will increase coverage by 0.49%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##             master    #302      +/-   ##
===========================================
+ Coverage     38.31%   38.8%   +0.49%     
- Complexity      932     941       +9     
===========================================
  Files           219     219              
  Lines          6921    6921              
  Branches        939     939              
===========================================
+ Hits           2652    2686      +34     
+ Misses         3937    3892      -45     
- Partials        332     343      +11

Impacted Files	Coverage Δ	Complexity Δ
...s/block/flow/controller/RateLimiterController.java	79.16% <0%> (-12.5%)	5% <0%> (-1%)
...a/com/alibaba/csp/sentinel/node/StatisticNode.java	67.21% <0%> (+1.63%)	22% <0%> (+1%)	⬆️
...a/csp/sentinel/slots/statistic/base/LongAdder.java	31.91% <0%> (+14.89%)	10% <0%> (+6%)	⬆️
...a/csp/sentinel/slots/statistic/base/Striped64.java	56.25% <0%> (+30.2%)	8% <0%> (+3%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update fba114d...bd2049b. Read the comment docs.