feat: support Anthropic API and add unit tests

[DavdGao]

The implementation includes the following files and classes:

• AnthropicChatModel in packages/agentscope/src/model/anthropic-model.ts
• Unit tests in packages/agentscope/tests/model/anthropic-model.test.ts

The expected functionalities to support:

• Streaming and non-streaming responses
• Tool calling API
• Tool choice

The unit tests should use mock responses to cover the following cases:

• call function with:
  • Streaming response with tool calling
  • Non-streaming response with tool calling
• _formatToolChoice method
• _formatToolSchemas method

Example implementation refers to dashscope and its unit tests