chore(deps): remove dependency on toolshed crate

[LNSD]

This pull request includes various changes to the project, focusing on removing dependencies and adding a new macro (copied from the toolshed crate). These changes will allow us to deprecate and remove the toolshed crate.

The most significant changes are listed below:

Macro addition:

• Added a new concat_bytes macro in src/bytes.rs to concatenate byte slices. The macro has been copied from the toolshed crate as the gateway is the only project using this unpublished crate.

Dependency updates:

• Removed the toolshed dependency from Cargo.toml.
• Removed the unused test-with dependency from Cargo.toml.

[Theodus]

Nice. Thanks!