fix credentialing field ordering and related singlesig-vlei-issuance test

[2byrds]

1. Fixes ordering of u field.
2. Modifies signed fetch to give the caller control over Request related args.
3. Improves reliability of singlesig-vlei-issuer test

[codecov]

Codecov Report

Attention: Patch coverage is 88.88889% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 82.82%. Comparing base (fddaff2) to head (4c728f1).
Report is 1 commits behind head on main.

❗ Current head 4c728f1 differs from pull request most recent head fc6d59b. Consider uploading reports for the commit fc6d59b to get more accurate results

Files	Patch %	Lines
src/keri/app/clienting.ts	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #254      +/-   ##
==========================================
+ Coverage   82.76%   82.82%   +0.06%     
==========================================
  Files          46       46              
  Lines        4218     4210       -8     
  Branches     1029     1049      +20     
==========================================
- Hits         3491     3487       -4     
+ Misses        722      694      -28     
- Partials        5       29      +24     

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[lenkan]

Cool! Much easier to review now. I don't understand the changes with the retries? Does the retry function not do this for you?

Also, if not too much effort, can the changes to signedFetch be separated to it's own PR to make it easier to review the history? I feel these are two unrelated changes.

[lenkan]

LGTM