[FEATURE] AmazonBedrockConfig dataclass should accept instance_profile_arn

[malanEvans]

Problem Statement
Now we can use an instance profile to authenticate access to Amazon Bedrock foundational models when we create model serving endpoints. However, python-sdk has not updated the relevant dataclass (AmazonBedrockConfig in databricks.sdk.service.serving) to support this.

Proposed Solution
Just include 'instance_profile_arn' in the dataclass as an optional attribute.

Additional Context
None.