feat(model): add ServerConfig and ClientConfig aliases - #1266

Motivation and Context

Follow-up to #1156. This PR introduces ServerConfig and ClientConfig as the recommended names for the values returned by ServerHandler::get_info and ClientHandler::get_info, and updates the ServerInfo and ClientInfo deprecation notes to point to them.

How Has This Been Tested?

Added tests

Breaking Changes

None

Public API Check is a false neative in CI. It does not check return types at all. A type alias is transparent, so a downstream fn get_info(&self) -> ServerInfo still satisfies a trait declared as -> ServerConfig. A newtype would have broken it, but an alias cannot.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed