Migrate test files from create_connected_server_and_client_session

Migrate the following files to use the new Client API:
- tests/server/fastmcp/test_server.py: Use Client.from_server(mcp) instead of
  client_session(mcp._mcp_server)
- tests/shared/test_session.py: Use InMemoryTransport + ClientSession for
  low-level session tests
- tests/shared/test_progress_notifications.py: Use InMemoryTransport for
  progress callback exception test
- examples/fastmcp/weather_structured.py: Use Client.from_server(mcp) for
  the example

The high-level Client API is used for tests that just need to call tools,
resources, and prompts. The low-level InMemoryTransport + ClientSession
pattern is used for tests that need direct session access (e.g., _in_flight,
send_notification, send_request).

Author: felixweinberger

examples/fastmcp/weather_structured.py

@@ -14,8 +14,8 @@
 
 from pydantic import BaseModel, Field
 
+from mcp.client import Client
 from mcp.server.fastmcp import FastMCP
-from mcp.shared.memory import create_connected_server_and_client_session as client_session
 
 # Create server
 mcp = FastMCP("Weather Service")
@@ -157,7 +157,7 @@ async def test() -> None:
         print("Testing Weather Service Tools (via MCP protocol)\n")
         print("=" * 80)
 
-        async with client_session(mcp._mcp_server) as client:
+        async with Client.from_server(mcp) as client:
             # Test get_weather
             result = await client.call_tool("get_weather", {"city": "London"})
             print("\nWeather in London:")