feat: include prompt_title with newspack_popup_id for data events

[laurelfulford]

All Submissions:

• Have you followed the Newspack Contributing guideline?
• Does your code follow the WordPress' coding standards and VIP Go coding standards?
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Changes proposed in this Pull Request:

This PR, along with Automattic/newspack-blocks#2271 and Automattic/newspack-popups#1508, adds the prompt_title to the modal checkout data events.

See Automattic/newspack-blocks#2271 for testing steps.

Closes # .

How to test the changes in this Pull Request:

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?