Doc needed: how to split logic across VUs

[MattDodsonEnglish]

This is an extremely common user question: users want to have one script that runs different logic depending on the test conditions. For example, this is one of the most linked-to forum posts: https://community.k6.io/t/how-to-distribute-vus-across-different-scenarios-with-k6/49/3

There are also a few ways to split logic across VUs:

• While loops using VU number
• Split into stages
• Using execution context variables to create a control flow (?)

A how-to guide could discuss situations when each way may be appropriate, then show example procedures.

[MattDodsonEnglish]

Idea for example use case: having active and inactive sessions, with some VUs logging in and doing things, and other VUs logging in and just sleeping.