Rename "gpu_ids" parameter to "worker_devices".

[Lucaweihs]

Problem

Currently the devices workers use is set by a "gpu_ids" dictionary entry in the machine_params method of a config file. This is a bit strange as these devices can (e.g. for debugging) be cpus.

Solution

Let's rename "gpu_ids" to something more evocative (e.g. "worker_devices" or "distributed_devices").

Dependencies

None.

Warnings

This will be a breaking change.

[Lucaweihs]

@jordis-ai2, @klemenkotar would be good to hear your feedback on this proposed change.

[jordis-ai2]

worker_devices sounds great to me (in engine we also use worker_id)