Rename the custom scan profiles feature flag

What does this MR do and why?

Rename the custom scan profiles feature flag

Rename custom_secret_detection_profiles_ui to custom_scan_profiles_ui,
across the definition file, the controller, group_scanners_overview and
both specs.

References

• flag added Add scan profile drawer to scanners overview (!252494 - merged)
• feature issue: [Frontend] Scan profile drawer: view, create, e... (#624191 - closed)

Screenshots or screen recordings

No visual changes expected

How to set up and validate locally

0. git checkout mfluharty-rename-custom-scan-profiles-ui-flag
   echo "Feature.enable(:custom_scan_profiles_ui)" | gdk rails c

1. have a GitLab Ultimate licence
2. go to a group => Secure => Security configuration
3. check that the scanners table shows:
   • a Manage profiles button on the Secret detection row
   • a View details button on every row
4. click Manage profiles and check that the profile drawer opens

with the flag off

5. turn it off:

   echo "Feature.disable(:custom_scan_profiles_ui)" | gdk rails c

6. reload Secure => Security configuration
7. check that:
   • no row has a Manage profiles button
   • View details is still on every row
   • the rest of the page is unchanged

the old name should be gone

8. check that nothing references the flag by its old name any more:
   • there is no custom_secret_detection_profiles_ui.yml under ee/config/feature_flags/
   • grep -rn "custom_secret_detection_profiles_ui\|customSecretDetectionProfilesUi" ee/ returns nothing

to run tests

yarn jest ee/spec/frontend/security_configuration/components/scan_profiles/group_scanners_overview_spec.js
bundle exec rspec ee/spec/requests/groups/security/configuration_controller_spec.rb

MR acceptance checklist

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