Gson generic call returns a JSON string by default

[finefuture]

What is the purpose of the change

1. GsonUtils provide toJson method, use same json util to write json
2. Gson generic call returns a JSON string by default

Brief changelog

Verifying this change

Checklist

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[AlbumenJ]

LGTM.
This is a breaking change and I have changed it to 3.3 branch.

[codecov-commenter]

Codecov Report

Merging #12633 (27993db) into 3.3 (48cc5b2) will increase coverage by 1.21%.
The diff coverage is n/a.

❗ Current head 27993db differs from pull request most recent head 2f21b6f. Consider uploading reports for the commit 2f21b6f to get more accurate results

@@             Coverage Diff              @@
##                3.3   #12633      +/-   ##
============================================
+ Coverage     68.19%   69.41%   +1.21%     
+ Complexity        6        2       -4     
============================================
  Files          1675     1629      -46     
  Lines         68928    67408    -1520     
  Branches      10039     9888     -151     
============================================
- Hits          47007    46791     -216     
+ Misses        17337    16100    -1237     
+ Partials       4584     4517      -67     

see 249 files with indirect coverage changes

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[sonarcloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
16 Code Smells

26.7% Coverage
0.0% Duplication

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