feat: index hint for CRDB when deleting identity credentials

[alnr]

Ref https://support.cockroachlabs.com/hc/en-us/requests/25430

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.59%. Comparing base (44eb305) to head (1182b14).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4276      +/-   ##
==========================================
+ Coverage   78.57%   78.59%   +0.01%     
==========================================
  Files         381      381              
  Lines       27376    27377       +1     
==========================================
+ Hits        21511    21517       +6     
+ Misses       4241     4237       -4     
+ Partials     1624     1623       -1     

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