Add support for tool annotations

[mattt]

This PR adds support for comprehensive tool annotations for better describing tool behavior, like whether it is read-only or destructive (modelcontextprotocol/modelcontextprotocol#185), added in the 2025-03-26 version of the MCP specification.

let searchTool = Tool(
    name: "web_search",
    description: "Search the web for information",
    inputSchema: [
        "query": ["type": "string", "description": "The search query"]
    ],
    annotations: .init(
        title: "Web Search",
        readOnlyHint: true,
        openWorldHint: true
    )
)