Add support for ephemeral resources

[pavelzw]

Terraform 1.10 comes with ephemeral resources. It would be great if the sops provider supported those s.t. the decrypted state isn't leaked in the state file.

https://www.hashicorp.com/blog/terraform-1-10-improves-handling-secrets-in-state-with-ephemeral-values
https://developer.hashicorp.com/terraform/plugin/framework/ephemeral-resources#add-ephemeral-resource-to-provider