fix(content-gating): account for block visibility in GA4 params

[dkoo]

All Submissions:

• Have you followed the Newspack Contributing guideline?
• Does your code follow the WordPress' coding standards and VIP Go coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Adds handling for content gate GA parameters to existing modal checkout GA events.

How to test the changes in this Pull Request:

See Automattic/newspack-plugin#3895

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?

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[github-actions]

Hey @dkoo, good job getting this PR merged! 🎉

Now, the needs-changelog label has been added to it.

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[matticbot]

🎉 This PR is included in version 4.11.0-alpha.1 🎉

The release is available on:

• npm package (@alpha dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[matticbot]

🎉 This PR is included in version 4.12.0-alpha.1 🎉

The release is available on:

• npm package (@alpha dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[matticbot]

🎉 This PR is included in version 4.12.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀