Request source vs multiple endpoints

Opening this issue as a place to discuss combining request sourcing & multiple endpoints.

*description*

Currently Nighthawk is able to hit multiple endpoints (feature 1) while using a request source (feature 2).

A convenient way to achieve this is through the file based request source plugin, where one can specify a few requests and then the software will loop over those. For those lacking context, see [here](https://github.com/envoyproxy/nighthawk/pull/637/files#diff-61ea2fb444801e3bac7bcf6f9b9034afd0f5c3e4d256509a04e60a210feb65e2) for an example.

When combining the two features, I think that if one specifies two endpoints and two request options in the traffic profile, this may then proceed to send request 1 consistently to endpoint one and request two to endpoint two.
This may not perfectly hold throughout a full execution, but I think chances are there will be skew.

Therefore I'm wondering if options to randomize selection of endpoints and/or request options would be prudent here.
That might be useful both for the independent options, but practically essential when combining the two.