Add feature flag `authentication_logs_migration_for_allowlist`

What does this MR do and why?

Creates the authentication_logs_migration_for_allowlist for #498125 (closed).

This FF is for allowing the user to auto-populate the job token allowlist using the authentication logs. This MR is just for creating the feature flag and the button for the auto-populate feature, which will not work at the moment. The feature will be further developed in future MRs.

References

Please include cross links to any resources that are relevant to this MR. This will give reviewers and future readers helpful context to give an efficient review of the changes introduced.

• [FE] Provide mechanism to migrate authenticatio... (#498125 - closed)
• [Feature flag] Rollout of `authentication_logs_... (#514159 - closed)

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Before	After
before	after

How to set up and validate locally

1. Enable the feature flag.

   Feature.enable(:authentication_logs_migration_for_allowlist)

2. Visit the Job token permissions section of the CI/CD settings. <path-to-project>/-/settings/ci_cd#js-token-access.
3. When the FF is disabled, the CRUD button displays Add group or project. This toggles the form for adding a group or project to the allowlist.
4. When the FF is enabled, the CRUD button will be replaced with an Add dropdown. The Add group or project item will toggle the same form as above.