Add Profile Selection to DAST Configuration Form

Related issues #330720 (closed), #330726 (closed)

• Designs - #276957 (closed)
• Feature epic - &5981 (closed)

What does this MR do?

This MR adds option to select Scanner & Site Profiles in DAST Security Configuration UI.

• Abstract out profile selectors logics from On-demand scans form.
• Creates a new component DastProfilesSelector for reusability

Follow-up tasks

• #335487 (closed): To move On-demand scans to use the new component
• #335486 (closed): To improve UX by caching selected profiles
• !65729 (closed): To add a slot to pass different help text when no profiles are created

Please note that these changes are behind feature flag dast_configuration_ui and documentation is being added via !63849 (merged).

Screenshots (strongly suggested)

with profiles	with no profiles

selected profile	selected conflicting profile

Error

How to test this

1. Enable the feature flag.

echo "Feature.enable(:dast_configuration_ui)" | rails c

1. Navigate to a project's Security Configuration page at /:namespace/:project/-/security/configuration.
   • You should see the Enable link in the DAST section.
   • Clicking on the link should take you to the empty DAST Settings page

Does this MR meet the acceptance criteria?

Conformity

• [-] I have included a changelog entry, or it's not needed. (Does this MR need a changelog?) (Changes are behind feature flag)
• [-] I have added/updated documentation, or it's not needed. ([Is documentation required?] (https://about.gitlab.com/handbook/engineering/ux/technical-writing/workflow/#when-documentation-is-required)) (It being added in !63849 (merged))
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.