feat: implement a way to stop crawler from the user function

[barjin]

This is a parity-tracking issue for this PR in Crawlee for Python: apify/crawlee-python#651

Currently, to stop the crawler instance, the users can only call the BasicCrawler.teardown() method, which is both undocumented (has the @ignore TypeDoc decorator) and not exactly named well.

The crawler.stop() implementation in Crawlee for Python forces the AutoscaledPool to not take any more tasks, but to gracefully finish the ones that are in currently in progress. This is different from the AutoscaledPool.abort method (called by crawler.teardown()), which according to the docstring abandons the running tasks on spot ("all running tasks will be left in their current state").

More context / discussion at https://apify.slack.com/archives/CD0SF6KD4/p1734526549266519