Add Actor.start_task() #1161

Actor has start() and call() for Actors, but only call_task() for tasks. To start a task without waiting for it, you have to use Actor.apify_client.task(task_id).start(), which skips what the wrapper adds: the token shortcut, timeout='inherit', webhook conversion, and run_name once #1149 is merged.

Add Actor.start_task() with the parameters of call_task() except wait, returning the started run. The client already has task.start().

JS parity issue: apify/apify-sdk-js#764

✍️ Drafted by Claude Code