Add a filter to the workshop request view to filter for requests with invalid member codes.

[maneesha]

This can happen after #2380 is implemented.
The view for workshop requests, inquiries, and self organized submissions should all include an option to filter by invalid member registration codes.
We should be able to edit this field just as we can edit other fields in those forms.

[elichad]

Closing this as won't complete, for two reasons:

1. the hard validation on the WRF reduces the need for this filter
2. I've added the important membership info directly to the WR details page as part of Add further checks for invalid code to workshop request forms #2553, so it will be readily visible as the team processes requests.