fix(form): Make dropdown display inside the modal with Button Mode

[mathetos]

User Story

As a Give user I want to use Button mode and have multi-levels displayed as a dropdown.

Current Behavior

Currently, the dropdown appears ABOVE the button in button mode. See sample here:

Expected Behavior

I expect the dropdown to appear inside the modal.

Steps to Reproduce

1. Create a form with multi-levels and set it to Button Only mode.
2. View it on the frontend and confirm that the dropdown appears ABOVE the button

Related

• Perhaps related issue: fix(donation): Modal and Button display modes improperly showing payment errors #3006
• Reported here: https://wordpress.org/support/topic/setting-form-display-to-button-only-displays-a-dropdown-above-button/
• See live example here: https://www.mattcromwell.com/give-test/

Tasks

• Ensure dropdown appears inside the modal in button mode
• double-check other modes as well
• Test with the Give Widget as well
• Test with a form that is not set to button mode by default, but use the shortcode builder to change the display mode and ensure the dropdown is STILL inside the modal.