Implement wait_for_all_requests_to_be_added for adding baches of requests

Implement adding requests in the background using asyncio.Task and wait for them in the drop() method.
Implement wait_for_all_requests_to_be_added parameter for:
- BasicCrawler.add_requests()
- RequestProvider.add_requests_batched()
- BaseStorageClient.batch_add_requests()

wait_for_all_requests_to_be_added: bool = False

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