Refactor Camunda registration options + drop RJSF

[sergei-maertens]

No ticket, follow up on #4806

Changes

• Removed wrappers around RJSF from Camunda registration options, otherwise it's left untouched
• Removed vendor workarounds
• Removed RJSF dependency

Checklist

Check off the items that are completed or not relevant.

• Impact on features

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

• Release management

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

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

  • [x] Ran ./bin/makemessages_js.sh
  • [x] Ran ./bin/compilemessages_js.sh

• Commit hygiene

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

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 96.55%. Comparing base (b96d2ae) to head (ef6cac1). Report is 4 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #4807 +/- ## ======================================= Coverage 96.55% 96.55% ======================================= Files 748 748 Lines 25423 25423 Branches 3362 3362 ======================================= Hits 24548 24548 Misses 610 610 Partials 265 265 ```

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