[#6106] Adapt admin form designer to the new type form field

[vaszig]

Closes #6106

Changes

• disable introduction page (see comment [OF#6144] Load the correct variant according to the form type open-forms-sdk#962 (comment))
• reset and hide login options
• ensure only one step can be added/configured
• prevent login requires on the single step
• allow registration
• allow logic (only the registration backends action for now)
• allow confirmation templates
• disable prefill (backend from submission and frontend in the variables tab, it's also disabled in the form builder)
• disable/hide progress indicator display
• disable submit options (always submit without overview)
• disable new form renderer (default to true)
• disable advanced configuration

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
  • Checked new model fields are usable in the admin
  • Problem detection in the admin email digest is handled

• Dockerfile/scripts

  • Updated the Dockerfile with the necessary scripts from the ./bin folder

• Commit hygiene

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

• Documentation

  • Added documentation which describes the changes

[vaszig]

Do NOT merge until 3.5 is released.
Requires #6102

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 97.07%. Comparing base (3b1326c) to head (038ed83).

Files with missing lines	Patch %	Lines
src/openforms/submissions/api/viewsets.py	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                              Coverage Diff                              @@
##           feature/6098-introduce-a-single-page-form    #6117      +/-   ##
=============================================================================
- Coverage                                      97.08%   97.07%   -0.01%     
=============================================================================
  Files                                            884      884              
  Lines                                          33393    33394       +1     
  Branches                                        2997     2998       +1     
=============================================================================
  Hits                                           32418    32418              
  Misses                                           658      658              
- Partials                                         317      318       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.