Add clippy and rustfmt setups to the Tuta SDK

[rezbyte]

We should implement a linting setup to help maintain code quality while writing the rust code for the SDK. I would suggest using cargo's included linter 'clippy' and enabling the lints in rustc. In order to come to a rule list we all agree upon, you could base the linting config on the discussions had in #6451.

On that note, we should also integrate a code formatter such as rustfmt. rustfmt is from the Rust team and is integrated with a number of editors including RustRover and VS Code, so I recommend it.

Both of the two above should have a GitHub Actions workflow to run them as checks on PRs.