Modernize CI Workflow

[LeWimbes]

This PR modernizes the CI workflow and expands the checks to improve coverage.

Summary of changes

• Bump actions/checkout to the latest version.
• Use actions-rust-lang/setup-rust-toolchain for simpler Rust setup and built-in caching.
• Introduce a job matrix to remove duplicated configuration.
• Expand Cargo commands.
• Add a documentation build step.
• Rename workflow file: rust-build-and-test.yml -> ci.yml (to align with cd.yml).
• Remove two whitespaces in security.rs to satisfy clippy.

[LeWimbes]

I intentionally left cd.yml untouched as I don't have much experience with CD setups and didn't want to risk breaking releases.
However, I wouldn't mind learning about (Rust) CD workflows. Let me know if you'd be interested in another PR regarding the CD workflow.