Provide total and lengthComputable data for xhr requests

Type: feature

The following has been addressed in the PR:

[ ] There is a related issue
[x] All code has been formatted with prettier as per the readme code style guidelines
[x] Unit or Functional tests are included in the PR

Description:

When specifically using the xhr provider, the upload events allow access to data available from the native xhr progress event:

const xhr = xhr.post('http://www.example.com/', {
    body: someLargeString
});

xhr.upload.subscribe(uploadData => {
  const { loaded, total, lengthComputable } = uploadData;
    if (lengthComputable) {
        const percentComplete = loaded / total * 100;
    }
});

The node provider has also been updated for consistency:

const req = request.post('http://www.example.com/', {
    body: someLargeString
});

req.upload.subscribe(uploadData => {
    const { loaded } = uploadData;
    // do something with uploaded bytes
})

dojo / core

Provide total and lengthComputable data for xhr requests #405