The codepath for AllAttributesNull was not correct for any nested object
types with collections, and should create single null values for the
correct NestingMode rather than a single object with null attributes.
Since there is no reason to descend into nested object types to create
nullv alues, we can drop the AllAttributesNull function altogether and
create null values as needed during ProposedNew.
The corresponding AllBlockAttributesNull was only called internally in 1
location, and simply delegated to schema.EmptyValue. We can reduce the
package surface area by dropping that function too and calling
EmptyValue directly.
This is part of a general effort to move all of Terraform's non-library
package surface under internal in order to reinforce that these are for
internal use within Terraform only.
If you were previously importing packages under this prefix into an
external codebase, you could pin to an earlier release tag as an interim
solution until you've make a plan to achieve the same functionality some
other way.