feat: implement new utility functions for CallToolResult and TextContent

[hashemix]

📌 Summary

This PR introduces a set of convenience constructor methods for the CallToolResult struct to simplify the creation of results with various content types. It also supports builder-style methods for attaching metadata and structured content.

This functionality was already available in previous schema versions and is now supported in the 2025_06_18 and draft versions as well, with a slightly updated function signature.

example:

let res_link = CallToolResult::resource_link(vec![ link1, link2  ]);

let text_result = CallToolResult::text_content(vec![ TextContent::from(goodbye_message) ])