AnthropicBedrock retry policy not consistent with Bedrock Response

[RonakPai]

The should_retry function defined here https://github.com/anthropics/anthropic-sdk-python/blob/main/src/anthropic/_base_client.py#L747 does not always correctly correspond with the errors that should be retried from the Bedrock server responses.

For example, while streaming response, it's possible to occasionally get the below error from Bedrock with status code 400. This would not be retried by the SDK, but should be.

Would it be feasible to allow the user to input their own should_retry function like they do for max_retries? Happy to open a PR here as well