Push Dependency Scanning scan profile flag

What does this MR do and why?

Push Dependency Scanning scan profile flag

Add the custom_scan_profiles_dependency_scanning_ui beta feature flag
and push it to the frontend from
Groups::Security::ConfigurationController, scoped to the root ancestor
group.

Related to https://gitlab.com/gitlab-org/gitlab/-/work_items/634032

References

• frontend MR, stacked on this one: Add Dependency Scanning to scan profile advance... (!262667)

Screenshots or screen recordings

Not needed. Nothing visible changes until the frontend merge request lands.

How to set up and validate locally

0. git checkout 634032-add-dependency-scanning-to-scan-profile-advanced-configuration

1. have a GitLab Ultimate licence
2. go to a group => Secure => Security configuration
3. in the browser console, check that gon.features.customScanProfilesDependencyScanningUi is false
4. enable the custom_scan_profiles_dependency_scanning_ui feature flag (in caproni or gdk)
5. reload the page and check that gon.features.customScanProfilesDependencyScanningUi is true

to run tests

bundle exec rspec ee/spec/requests/groups/security/configuration_controller_spec.rb

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #634032