Use terraform-json StateOutput for Output method return value

[prksu]

Currently, the Output method terraform output -json returns a map with its own type value i.e. OutputMeta

https://github.com/hashicorp/terraform-exec/blob/3fe5e310fd57434fdb99157c26d6dd1241c2b618/tfexec/output.go#LL39C73-L39C94

according to the project description, terraform-exec return value should use the data type defined in terraform-json which has the fit type for this case i.e. StateOutput