chore(new_relic sink): add distribution support and send metric type

[tobz]

In the new_relic sink, among other issues, we currently do not support distributions even though they're supported on the New Relic side. Additionally, we don't send the metric type, which causes all metrics -- counter or gauge -- to be treated as gauges.

We should:

• [ ] #13902
• [ ] #13903
• [x] #13904

[jszwedko]

cc/ @asllop . I know you contributed the initial new_relic sink so just flagging this in case it is something you are interested to contribute.

[asllop]

@jszwedko yes I am! Also interested in https://github.com/vectordotdev/vector/issues/13377, I just don't know when I'm gonna have time to contribute.