Add setAttributes to make it easier to add them in bulk.

[rochdev]

Is your feature request related to a problem? Please describe.

In JavaScript, it's much easier to use a map-style object to add multiple attributes at once. Having to call setAttribute multiple times is thus unnecessary and requires more code, especially if copying from an existing object.

Describe the solution you'd like

It should be possible to add multiple attributes using a single call.

For example:

span.setAttributes({
  'http.method': 'GET',
  'http.path': '/foo/bar'
})

span.setAttributes(existingObject)