Add missing search fields and optimization to appointment info admin

[sergei-maertens]

No ticket, I noticed this when I was debugging something and just found out I have a spare branch lying around.

Changes

• Optimized admin for ApointmentInfo model.
• Improved being able to find a particular appointment info record with some search fields.

Checklist

Check off the items that are completed or not relevant.

• Impact on features

  • Checked copying a form
  • Checked import/export of a form
  • Config checks in the configuration overview admin page
  • Problem detection in the admin email digest is handled

• Release management

  • I have labelled the PR as "needs-backport" accordingly

• I have updated the translations assets (you do NOT need to provide translations)

  • Ran ./bin/makemessages.sh
  • Ran ./bin/compilemessages_js.sh

• Commit hygiene

  • Commit messages refer to the relevant Github issue
  • Commit messages explain the "why" of change, not the how

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.12%. Comparing base (dfa0d2c) to head (d1769d2).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4286   +/-   ##
=======================================
  Coverage   96.12%   96.12%           
=======================================
  Files         730      730           
  Lines       23502    23504    +2     
  Branches     2757     2757           
=======================================
+ Hits        22591    22593    +2     
  Misses        645      645           
  Partials      266      266           

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