Highlight paid features during active trial - Part 2 [RUN ALL RSPEC] [RUN AS-IF-FOSS]

What does this MR do?

Adds the experiment-type feature flag needed to enable the “Highlight Paid Features During Active Trial” experiment.

Related MRs

MR	Description
!56155 (merged)	Initializes the experiment, without a feature flag, and creates the badge component
!58834 (merged)	👈 You are here
!58827 (merged)	Adds the popover with more information but no CTAs

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because this experiment is behind a feature flag.
• [-] 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 #273626 (closed)