Spring-ai Add multimodal support to Bedrock Converse integration

The Bedrock Converse integration should support multimodal inputs including documents (PDF, DOC, etc.), images (JPEG, PNG, etc.), and videos (MP4, MOV, etc.). This will enable users to interact with the Bedrock AI models using various media types. Update BedrockProxyChatModel to handle multimodal content

Related: AWS Bedrock Multimodal API documentation

Comment From: tzolov

Resolved by #1888