Support for heterogeneous workload benchmarking

[fuji-184]

Hey! I was thinking it’d be awesome if we could benchmark two or more endpoints at the same time. Real world traffic isn't linear or limited to a single endpoint at a time, but the app handle multiple endpoints simultaneously. So to get more accurate data that really reflects real world scenario, we need the ability to benchmark multiple endpoints (e.g., /json, /db, /fortune) at the same time. This would help us see how the framework actually handles diverse, simultaneous loads. Would love to see this implemented.

[p8]

There is a similar issue: #9391