Harmonize DAST profiles mocks for frontend testing

What does this MR do and why?

This creates a few frontend fixtures to mock DAST profiles data. Those news mocks replace manual mocks that used to be defined in ee/spec/frontend/on_demand_scans_form/mocks/mock_data.js and ee/spec/frontend/security_configuration/dast_profiles/mocks/mock_data.js.

How to set up and validate locally

1. Make sure the required services are running:

    gdk start postgresql redis

2. Generate the fixtures:

   bundle exec spring rspec ee/spec/frontend/fixtures/dast_profiles.rb

3. Run the frontend specs:

   yarn jest on_demand_scans dast_profiles -w 1

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #288337 (closed)