Add invite members button the project empty state

What does this MR do?

• Add functionality when experiment is enabled on .com.
  • Adds Invite members button and text to empty project state as designed
  • Fires tracking events as described in tracking details
  • adds user to experimentation user group in controller.

Note: No changelog since behind an experiment/ff

How to test locally

• Create new empty/blank project.
• Append ?force_experiment=invite_members_empty_project_version_a to the URL and reload like this http://127.0.0.1:3000/root/dfdf?force_experiment=invite_members_empty_project_version_a

Screenshots (strongly suggested)

Platform	User in experiment	User not in experiment(no change)
desktop
mobile

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Related to #262014