HttpEndpointConfiguration doesn't support Secrets Manager secret

### Name of the resource

AWS::KinesisFirehose::DeliveryStream

### Resource name

_No response_

### Description

The `HttpEndpointConfiguration` property currently requires passing in a string for the `AccessKey` prop. That doesn't really work so well with the CDK. Support for a Secrets Manager secret would be really helpful please :) We're sort of blocked on using this until Secret support is there :( I'm guessing this might require some update to the Firehose API, so maybe you could pass this message onto that team please 🙏 Thanks!

### Other Details

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-kinesisfirehose-deliverystream-httpendpointconfiguration.html

Start with the AWS CloudFormation documentation for AWS::KinesisFirehose::DeliveryStream and its HttpEndpointConfiguration property, linked in the issue. Confirm whether the Firehose API supports a Secrets Manager secret for AccessKey and identify the required CloudFormation coverage change; done means the resource accepts and resolves that secret configuration.

Written by the indexing model from the issue text.