Test that accessing the `processed` property of a text field with a prop expression actually returns the filtered text

Overview

If you access a formatted text field with a dynamic prop expression, you would probably want to use the processed computed property, to ensure that the text is filtered and sanitized. This should work, in theory, but we should explicitly test it.

Proposed resolution

We could probably do this by altering NodeTemplatesTest, which already accesses a processed text value.