Add query string as a configurable tag on http.url

[bsamsom]

There was previously a version of dd-trace-js that set the query string on the http.url tags, in the pr the removed it https://github.com/DataDog/dd-trace-js/pull/531

It was mentioned that it would be readded as a configurable option in the future, I'd like to get that added if possible, reading through the docs and peaking at the code it looks like it has yet to be re-added as an optional feature.

[bsamsom]

not necessary for the above but it might also be nice to parse the query string into key-value pairs as the Url Parser does on logs. https://docs.datadoghq.com/logs/log_configuration/processors/?tab=ui#url-parser