Spring-ai AWS Bedrock add Cohere Command R model support.

AWS Bedrock Cohere Command R release link: https://aws.amazon.com/about-aws/whats-new/2024/04/cohere-command-r-r-plus-amazon-bedrock/

Cohere Command R model request and response body format is different than Cohere, so I create a new BedrockCohereCommandRChatClient client.

Here is the request body documentation: https://docs.aws.amazon.com/bedrock/latest/userguide/model-parameters-cohere-command-r-plus.html

Comment From: maxjiang153

Hi @tzolov pls check this PR, I've updated the Cohere Command R model from ChatClient to ChatModel and added exponential backoff support.

AWS Bedrock Cohere Model supports Function calling, if this PR can be merged, I'll create a new PR for function calling

Comment From: maxjiang153

re-implement with: https://github.com/spring-projects/spring-ai/pull/813