Forms - add an option for Other to the Signer Selection screen for any dynamic form signer type

For instance, if this option is enabled for a Teacher signer type, the person submitting the form would be able to specific a First Name, Last Name, and email address the same way that this works if no guardian records are found. Alternatively, make this work the same way that it currently does for teachers.

The use case here is a Teacher Recommendation form assigned to a Student Application as a question type. While most students will be able to choose from a list of their teachers, students form outside the district would need to specify a teacher. Also, students may want a recommendation from a teacher that we no longer have a record of.