Add pipeline validator to check identity verification

What does this MR do and why?

As part of Iteration 1 for identity verification, this MR introduces the backend functionality to block a pipeline if a user has not yet verified their identity.

Closes: https://gitlab.com/gitlab-org/modelops/anti-abuse/team-tasks/-/issues/669

MR acceptance checklist

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

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Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Start GDK with SaaS simulation

   $ export GITLAB_SIMULATE_SAAS=1
   $ gdk start

2. Ensure that you have a runner setup in GDK.

3. Enable the relevant feature flags and configure the required settings

   > Feature.enable(:opt_in_identity_verification)
   > Feature.enable(:identity_verification_phone_number)
   > Feature.enable(:ci_requires_identity_verification_on_free_plan)

4. Setup Telesign

   > ApplicationSetting.first.update(telesign_customer_xid: '<value_is_in_1Pass>', telesign_api_key: '<value_is_in_1Pass>')

   Credentials are in 1Password under Telesign API Keys (use GITLAB - DEVELOPMENT)

5. Update ee/app/models/concerns/identity_verifiable.rb to skip the check to ensure a user was created after the release date.

   diff --git a/ee/app/models/concerns/identity_verifiable.rb b/ee/app/models/concerns/identity_verifiable.rb
   index 8db2775658db..990f022cd4bf 100644
   --- a/ee/app/models/concerns/identity_verifiable.rb
   +++ b/ee/app/models/concerns/identity_verifiable.rb
   @@ -279,7 +279,7 @@ def identity_verification_exemption_attribute
      end
   
      def user_has_restrictions?
   -    created_at > NEW_USER_RESTRICTIONS_RELEASE_DATE
   +    true
      end
   
      def project_requires_identity_verification_for_pipelines?(project)

6. Login with a new user

7. Attempt to trigger a pipeline. This should be blocked with an error due to identity verification.

8. Navigate to http://gdk.test:3000/-/identity_verification and verify a phone number.

9. Attempt to trigger a pipeline again. The pipeline should be created successfully.