feat!: make rust-mcp-sdk the sole dependency

[hashemix]

📌 Summary

Make rust-mcp-sdk the sole dependency—no need to add rust-mcp-schema separately anymore.

This PR updates the rust-mcp-sdk ecosystem to make rust-mcp-sdk the sole dependency required for users, eliminating the need to separately include rust-mcp-schema.

Macro generation logic in rust_mcp_macros also updated to adapt to the context of rust-mcp-sdk usage while maintaining compatibility for standalone rust_mcp_macros users with a new sdk cargo feature.

✨ Changes Made

• Added an sdk feature flag in rust_mcp_macros's Cargo.toml. Modified rust_mcp_macros to conditionally adapt its generated code based on the sdk feature, ensuring seamless integration with rust-mcp-sdk while keeping it compatible with rust-mcp-schema.
• Ensured rust-mcp-sdk re-exports rust-mcp-schema as rust_mcp_sdk::schema for ergonomic access to schema types (e.g., rust_mcp_sdk::schema::Tool);
• Updated documentation in READMEs to clarify dependency requirements and usage.
• Removed rust-mcp-schema dependency from examples and updated them to use re-exported rust_mcp_sdk::schema instead