Add buyer data to analytics where it's available

[kelvin-chappell]

This expects bid responses to have buyer data in the format specified in prebid#3115 if there is any buyer data in the response.

The first bidder we integrated, Pubmatic, was done before a standard emerged. So the fields read are different. That means there will need to be a transition from the old fields to the new ones:

1. Where the field is changing, read from both giving preference to the new field.
2. Update the pubmatic bid response to use the new field.
3. Update the analytics adapter to use only the new field.