Fix: reCAPTCHA v3 validation could prevent checkout with offsite gateways.

* New: Checkout fields can be displayed using conditional logic.

* New: The reCAPTCHA field now supports reCAPTCHA v3 for frictionless validation.

* Improvement: The checkout form file upload now uses the native file input.

* Improvement: Required fields use HTML5 attributes to ensure they are marked required.

* Improvement: Form fields markup has been updated for validity and accessibility.

* Improvement: The checkout form editor is now correctly registered as a submenu item under Downloads.

* Improvement: Form styles have been updated for improved layout and mobile responsiveness.

* Improvement: The form builder has been updated for improved accessibility and more modern styling.

* Fix: In EDD 3.0, updating an order in the admin did not update custom checkout fields.

* Fix: Media uploader resources were being loaded even when not needed.

* Fix: In some cases, the date picker was not usable.

* Fix: Compatibility scripts were preventing tooltips (such as native HTML5 validation) from displaying correctly.

* Dev: Getting an attachment ID from a URL now uses the core WordPress function.

* Dev: Update how licensing is instantiated.

* Dev: Refactor how the plugin is booted and checks for requirements.

* Dev: Improved PHP 8 compatibility.

* Fix: Unable to save custom fields to user metadata when using Auto Register.

* Fix: Unexpected results when a user and payment have the same ID.

* Fix: Unnecessary `<span>` element being added to the user info fieldset.

* Refactor: Update functions used for the Commissions integration.

* Dev: Compatibility with EDD 3.0.