Some AttributeDefinition instances are configured with default values but say they are required

An AD with a default value does not require the user to set it, so configuring it with required = true fka allowNull = false is incorrect. WFCORE-2252 proposes to reject these. This is to clean them up first.

Note that for any such attributes, if they existed in a previous release a transformer must be written to go along with a change to required=false. Even though they had a default before, the required=true setting made it as if it didn't exist, so this change is the same as adding a default