[BUGFIXING] User Fields Incorrectly Marked as Required During Checkout Despite Being Unset Using pmpro_required_user_fields Filter

[MaximilianoRicoTabo]

• Add a helper function that takes field name and field type and based on globals required fields, that can be filtered, return an array with values to build the field HTML block
• Pull values for each field and build the block based on this.
• Remove jQuery code that add required stuff without take into consideration filtered required fields.

All Submissions:

• Have you followed the Contributing guideline?
• Does your code follow the WordPress' 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:

Instead of adding required css clases, asterisks and aria attributes after checkout page DOM's load with jQuery, build blocks in the server side bringing the info from a helper function based on field name, field type and global required fields ( after potentially filtered ).

Resolves #3165 .

How to test the changes in this Pull Request:

1. Apply the patch
2. Create a snippet filtering pmpro_required_billing_fields and pmpro_required_user_fields and try setting and unsetting different fields.
3. Observe that required UI stuff is added or not based on filtered required fields.

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you successfully run tests with your changes locally?

Changelog entry

Enter a summary of all changes on this Pull Request. This will appear in the changelog if accepted.