Preprints: Add support for read-only custom fields

Is your feature request related to a problem? Please describe.
As a preprints administrator, I want to be able to collect and store certain metadata about a preprint via custom fields, but not have those fields display to the submitting author in the submission form or author dashboard view page.

For example, such fields could be house metadata about the API client which added a preprint to Janeway repository.

Describe the solution you'd like
Add a new ticky box option to the custom field setup page: Read Only

Authors do not see "Read Only" fields during the submission process, nor on their author dashboard.

Managers and administrators/staff can see and update the fields in the /repository/manager/XXXX page.

Additional context

Start at the custom field setup page and trace how fields are shown in the submission form, author dashboard view, and /repository/manager/XXXX page. Check the existing custom-field handling and permissions before defining the change. Done means a Read Only option hides fields from authors while allowing managers and administrators/staff to view and update them.