[R] Support for Tensor class

It would be nice to have support for the [Tensor class](https://arrow.apache.org/docs/cpp/api/tensor.html#dense-tensors) in the R package. 

I'm interested in using it for a reliable way to transfer torch tensors between R sessions.

I can submit a PR in a few days for discussion.

Thanks very much!

**Reporter**: [Daniel Falbel](https://issues.apache.org/jira/browse/ARROW-11636)

_{**Note**: *This issue was originally created as [ARROW-11636](https://issues.apache.org/jira/browse/ARROW-11636). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

Start by reading the Arrow C++ Tensor class documentation linked in the issue and inspect how the R package currently represents transferable data. Compare the requirements for moving torch tensors between R sessions with the Tensor API. Done means the R package supports Tensor values with coverage for that transfer use case.

Written by the indexing model from the issue text.