build: add rustfmt and clippy to toolchain components

[niStee]

What does this PR do

This PR adds rustfmt and clippy to the components list in rust-toolchain.toml.

Because CONTRIBUTING.md requires contributors to run cargo fmt and cargo clippy locally before submitting a PR, adding them to the toolchain configuration ensures that anyone working on the project will automatically have the correct tools installed via rustup. This improves developer experience without relying on auto-fixing CI or external dependencies.

Standards checklist

• The PR title is descriptive
• I have read CONTRIBUTING.md
• Optional: I have tested the code myself, with the relevant tools installed. If yes, add Topgrade's output of the relevant steps.
• If this PR introduces new user-facing messages they are translated

AI involvement

I consulted an AI assistant to discuss the security implications of auto-fixing formatting in CI. After discovering that CI auto-fixes with PATs introduce security vulnerabilities for outside contributors, the AI suggested making this clean, local toolchain change instead.

[GideonBear]

Can you show that this improves the developer experience? The default components to install include clippy and rustfmt, so any commands executed here will install all of them at the same time.