feat: support passing AKSK to the bedrock client

[fengxu1211]

support passing AKSK to the bedrock client for invoking LLM from another account.

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Description

This pull request includes modifications to the configuration file for the infrastructure bin, the chat stack definition, shared types, and the Langchain integration for the online chat models. The changes aim to improve the overall functionality and performance of the chat system.

Type of change

• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

File Stats Summary

File number involved in this PR: 4, unfold to see the details:

The file changes summary is as follows:

Files	Changes	Change Summary
source/infrastructure/lib/shared/types.ts	2 added, 0 removed	The code adds optional properties bedrockAk and bedrockSk to the chat object in the SystemConfig interface.
source/infrastructure/bin/config.ts	2 added, 0 removed	The code adds two new configuration properties, 'bedrockAk' and 'bedrockSk', to the chat object in the SystemConfig, likely for authentication purposes.
source/infrastructure/lib/chat/chat-stack.ts	2 added, 0 removed	This code change adds environment variables for AWS access key and secret access key for Bedrock integration to the ChatStack Lambda function.
source/lambda/online/common_logic/langchain_integration/chat_models/bedrock_models.py	27 added, 8 removed	The code changes add the ability to use AWS access key and secret access key from environment variables to initialize the ChatBedrockConverse model, in addition to the existing method of using a credentials profile name.