Fix EZP-20696: REST v2: Not possible to create content with an ezbinaryfile

JIRA: https://jira.ez.no/browse/EZP-20696

# Description

When creating a content with an ezbinaryfile field, the REST API returns an error 406. This patch fixes this by registering the BinaryProcessor for the ezbinaryfile field type. This also fixes the issue where the output struct for ezbinaryfile fields does not contain anything that allows to retrieve the file in the field.

# Tests

manual test + unit tests