unified nacos user and password obtaining path

[binbin0325]

What this PR does:
The user name and password of nacos are obtained from the configuration, not from param
Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[codecov-commenter]

Codecov Report

Merging #1645 (27efe5e) into 3.0 (0603eed) will increase coverage by 0.10%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              3.0    #1645      +/-   ##
==========================================
+ Coverage   41.04%   41.15%   +0.10%     
==========================================
  Files         253      253              
  Lines       14501    14506       +5     
==========================================
+ Hits         5952     5970      +18     
+ Misses       7860     7845      -15     
- Partials      689      691       +2     

Impacted Files	Coverage Δ
config/config_center_config.go	50.48% <100.00%> (+0.48%)	⬆️
config_center/nacos/impl.go	75.24% <100.00%> (ø)
metadata/report/nacos/report.go	40.00% <100.00%> (+1.76%)	⬆️
metadata/report/delegate/delegate_report.go	35.09% <0.00%> (+8.60%)	⬆️

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