fix: dumpConfig support circular json

[dead-horse]

Checklist

• npm test passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

Affected core subsystem(s)

Description of change

https://www.npmjs.com/package/circular-json is widely used

[codecov]

Codecov Report

Merging #2394 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2394      +/-   ##
==========================================
+ Coverage   99.61%   99.61%   +<.01%     
==========================================
  Files          29       29              
  Lines         783      784       +1     
==========================================
+ Hits          780      781       +1     
  Misses          3        3

Impacted Files	Coverage Δ
lib/egg.js	100% <100%> (ø)	⬆️

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