[ifrt] NFC: Use PjRtFuture<absl::StatusOr<T>> in ifrt
[ifrt] NFC: Use PjRtFuture<absl::StatusOr<T>> in ifrt

In preparation for making PjRtFuture holding absl::StatusOr<T> payload add StatusOr to all existing PjRtFuture<T>. It will be removed later when all users will use absl::StatusOr wrappers.
