Update workflows & cargo lockfile

[Neotamandua]

This pull request updates the GitHub Actions workflow configuration for Rust formatting, linting, and dependency checks. The main goals are to modernize the workflow, improve caching for faster runs, and use updated actions for better reliability.

Workflow modernization and improvements:

• Updated all jobs (rustfmt, clippy, and deny) to use newer versions of GitHub Actions (actions/checkout@v4 and EmbarkStudios/cargo-deny-action@v2) for improved performance and compatibility.
• Switched Rust toolchain installation to use dtolnay/rust-toolchain action for both nightly and stable toolchains, simplifying setup and ensuring consistency.

Clippy job enhancements:

• Added a step to cache the Cargo registry and build artifacts, speeding up subsequent workflow runs.
• Configured Clippy to run on all targets and features for more comprehensive linting coverage.

General improvements:

• Added descriptive job names for better readability in the Actions UI.
• Updated the cargo-deny job to specify the Rust version explicitly, ensuring compatibility.

[Copilot]

Pull Request Overview

Updates GitHub Actions workflow configuration to use more recent action versions and improve the CI pipeline structure with better caching and clearer step names.

• Updated action versions from v3 to v4 for checkout and other actions
• Improved workflow structure with descriptive job and step names
• Added Cargo registry caching to improve build performance

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[SplittyDev]

LGTM 👍