Verify all fields store values in the declared type

Mongoid permits applications to declare field types. However it does not always ensure the values written to the fields are of the declared type.

This was an issue previously for regexp fields (https://jira.mongodb.org/browse/MONGOID-4668) and this came up again for time fields (https://github.com/mongodb/mongoid/pull/5245).

This ticket is to investigate all of the defined field types, verify that they store values in the declared type, and to create follow-up tickets for types that need to be corrected.