Can't filter objects with missing date field values

[nniehoff]

Environment
Python version: Any
Nautobot version: 1.3.2
Any objects with date fields can't be filtered to search those with missing values.

This is related to #795. While most fields you can now search with "null" to find objects with missing values if the field is a date field the UI will not let you enter "null" and if you change the URL to include ?cf_date_field=null the filter is not applied. The easiest way to reproduce this is with a custom date field which is allowed to be null.

Expected Behavior

Only objects with missing (empty) value in a given date (custom or otherwise) fields should have been returned.

Observed Behavior

All objects were returned regardless of the date field.

[jathanism]

Related to #1905

[gsnider2195]

May be solved by #2126