Agentic - MCP and A2A Support Library in Rust

EXPERIMENTAL: This is an experimental library at this point, but the goal is to become a support library for implementing MCP and Agent-to-Agent Services and Clients.

The current objectives are:

• agentic::mcp provides types to support the MCP Client and Server Protocols.

• agentic::a2a (coming later) provides types to support the A2A Client and Server Protocols.