update nacos namespace demo and update nacos-sdk version

[yanlinly]

Describe what this PR does / why we need it

update nacos namespace demo and update nacos-sdk version to 0.8.0 (pre-ga version), so that more stable, and learn namespace feature.

Does this pull request fix one issue?

no

Describe how you did it

update demo

Describe how to verify it

run this demo

Special notes for reviews

you can learn how to use namespace by this demo

[codecov-io]

Codecov Report

Merging #474 into master will increase coverage by 0.61%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #474      +/-   ##
============================================
+ Coverage      39.4%   40.01%   +0.61%     
- Complexity     1058     1072      +14     
============================================
  Files           236      236              
  Lines          7538     7538              
  Branches       1049     1049              
============================================
+ Hits           2970     3016      +46     
+ Misses         4187     4130      -57     
- Partials        381      392      +11

Impacted Files	Coverage Δ	Complexity Δ
...s/block/flow/controller/RateLimiterController.java	79.31% <0%> (-10.35%)	7% <0%> (-1%)
...a/csp/sentinel/slots/statistic/base/LongAdder.java	36.17% <0%> (+19.14%)	12% <0%> (+8%)	⬆️
...a/csp/sentinel/slots/statistic/base/Striped64.java	67.7% <0%> (+41.66%)	12% <0%> (+7%)	⬆️

---

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 f27d7a4...4b096e0. Read the comment docs.

[sczyh30]

LGTM

[sczyh30]

Thanks!