Stabilize k6/experimental/csv module

[oleiade]

In v0.54, we introduced an experimental k6/experimental/csv module in k6.

Experimental modules intend to become part of the engine of k6 eventually. We intend to eventually have the csv module become part of the engine too: and being importable as k6/csv.

However, the current state of the module is that we're still trying to figure out what the best API could be, and ensure it covers the majority of use cases our users encounter.

As a result, this issue intends to define the steps left to complete to reach a state that we deem acceptable for the csv module to become stable.