Update all FastMCP examples to use mcp.server.fastmcp instead of fastmcp.
Add tests to verify example servers work correctly.
Changes:
- Update import paths in all example files
- Create test_examples.py to verify functionality
- Fix test assertions to match actual response format
- Update type hints to use Python 3.10 syntax (dict, list, X | None)
- Replace requests with httpx for HTTP client consistency
- Improve async context management using AsyncExitStack
- Simplify server cleanup method