Support conditional fields where the fields are on different form modes

Problem/Motivation

This module does not work unless the control field and the target field both appear on the same form display mode.

Steps to reproduce

Create an entity type with at least two form display modes. Place the control field on one and the target field on the other. Observe that the conditions do not work.

Proposed resolution

Implement the conditions in PHP so that the access to the target field respects the conditions that have been configured even when the control field is not displayed on the current form display mode.

Remaining tasks

Implement.

User interface changes

None.

API changes

None.

Data model changes

None.