feat!: add support for multiple active schema versions

[hashemix]

📌 Summary

This PR introduces support for enabling multiple MCP Protocol schema versions concurrently. While one version is designated as the default, additional versions can be activated via feature flags and accessed through clearly named modules.

✨ Changes Made

• Introduced versioned internal module names to avoid conflicts
• Non-default schemas are now accessible via modules such as:
  • rust_mcp_schema::mcp_2024_11_05
  • rust_mcp_schema::mcp_draft

💡 Additional Notes

• The default schema version remains enabled by default.