Inserting a null default value on a `not null` column does not return correct error message

The correct error message should be `Field '[col name]' doesn't have a default value` but we instead return `column name '[col name]' is non-nullable but attempted to set a value of null`

We currently have some skip tests for this. Link to this bug added to those tests in dolthub/go-mysql-server#3705

Start by locating the skip tests referenced in dolthub/go-mysql-server#3705 and trace the implementation that produces the current non-nullable-null error. Update the behavior so inserting a null default into a not-null column returns the expected “Field '[col name]' doesn't have a default value” message, then use those tests to verify the result.

Written by the indexing model from the issue text.