core: don't advertise data source destroy via hooks
core: don't advertise data source destroy via hooks

The fact that we clean up data source state by applying a "destroy" action
for them is an implementation detail, and so should not be visible to
outside callers or to the user.

Signalling these as real destroys creates confusion for users because
they see Terraform say things like:

    data.template_file.foo: Refreshing state..."

...which, to an understandably-nervous sysadmin, might make them suspect
that the underlying object was deleted, rather than just Terraform's
record of it.

hashicorp/terraform-plugin-sdk,hashicorp/terraform-plugin-sdk