FE: Create "Role" selection

Why are we doing this work

• Users want to be able to select a role to be an approver

Relevant links

• Design Issue
  • 

Implementation plan

• MR 1: Part 1
• backend Create the :scan_result_role_action feature flag yaml and pass it up on the group and project policy controllers
• frontend Copy scan_result_policy/policy_action_builder.vue to .../security_orchestration/components/policy_editor/scan_result_policy/policy_action_builder_v2.vue
• frontend Conditionally render the action components in scan_result_policy/scan_result_policy_editor.vue based on the feature flag
• MR 2: Part 2
• frontend Modify the action message to include a dropdown that includes role or individual users or groups
• frontend for project-level, request roles and their numbers for projects
• frontend for group-level, pass up Gitlab::Access.sym_options_with_owner and use that to populate dropdown

Verification steps

1. Upload a GitLab Ultimate license
2. Enable the :scan_result_role_action feature flag with the below command

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

3. Navigate to a project/group => Security & Compliance => Policies => New policy => Scan Result Policy
4. Verify a user can select a Role in the Actions area