[Backport 2.x] [MD]Use placeholder for data source credentials fields when export saved object

[opensearch-trigger-bot]

Backport 0188efe from #6928.

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.48%. Comparing base (b7200e7) to head (fc24864).

Additional details and impacted files

@@            Coverage Diff             @@
##              2.x    #6931      +/-   ##
==========================================
+ Coverage   67.47%   67.48%   +0.01%     
==========================================
  Files        3442     3442              
  Lines       67872    67884      +12     
  Branches    11027    11031       +4     
==========================================
+ Hits        45798    45814      +16     
+ Misses      19410    19406       -4     
  Partials     2664     2664              

Flag	Coverage Δ
Linux_1	33.10% <7.69%> (-0.01%)	⬇️
Linux_2	55.17% <100.00%> (+0.02%)	⬆️
Linux_3	45.27% <7.69%> (?)
Linux_4	34.95% <7.69%> (-0.01%)	⬇️
Windows_1	33.12% <7.69%> (-0.01%)	⬇️
Windows_2	55.14% <100.00%> (+0.03%)	⬆️
Windows_3	45.28% <7.69%> (-0.02%)	⬇️
Windows_4	34.95% <7.69%> (-0.01%)	⬇️

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