Cleanup the existing secret field functionality

[andrewballantyne]

https://issues.redhat.com/browse/RHOAIENG-14314

Description

Couple PR followups to the previous effort to add DB field to trusty startup

How Has This Been Tested?

See #3305 for setup. Basically this is all frontend so you just need trusty enabled and to interact with the UI modal for configuring it.

Test Impact

None, UI quirks.

Request review criteria:

Self checklist (all need to be checked):

• The developer has manually tested the changes and verified that the changes work
• Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has added tests or explained why testing cannot be added (unit or cypress tests for related changes)

If you have UI changes:

• Included any necessary screenshots or gifs if it was a UI change.
• Included tags to the UX team if it was a UI/UX change.

After the PR is posted & before it merges:

• The developer has tested their solution on a cluster by using the image produced by the PR to main

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.77%. Comparing base (0c15247) to head (4bd5837).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3327      +/-   ##
==========================================
- Coverage   84.81%   84.77%   -0.05%     
==========================================
  Files        1315     1315              
  Lines       29517    29518       +1     
  Branches     8060     8061       +1     
==========================================
- Hits        25036    25024      -12     
- Misses       4481     4494      +13     

Files with missing lines	Coverage Δ
...s/trustyai/content/TrustyDBExistingSecretField.tsx	87.50% <100.00%> (+0.40%)	⬆️

... and 5 files with indirect coverage changes

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[Gkrumbach07]

/lgtm

[openshift-ci]

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