feat(cli): data integrity commands

[adekbadek]

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 CLI command for handling data integrity:

• wp newspack-network fix-roles
• wp newspack-network get-user-memberships
• wp newspack-network fix-membership-discrepancies
• wp newspack-network fix-registration-based-memberships
• wp newspack-network display-user-discrepancies
• wp newspack-network deduplicate-users
• wp newspack-network fix-subscriptions
• wp newspack-network reprocess-events

How to test the changes in this Pull Request:

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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?