bump rust edition to 2024

[Panaetius]

note that env::set_var and env::remove_var are unsafe in rust 2024, not because of Rust, but because the underlying Posix implementation is unsafe (so it's already unsafe in rust 2021, just not marked as such).

The whole code for setting log env var is weird anyways, since we already used env_logger which has config for setting the log level. I've switched to using that and also using clap-verbosity-flag which is purpose built by the clap devs for handling -v in conjuction with env_logger.

renamed gen to generator since gen is now a reserved keyword (for gen fn iterator functions, like python iterator functions with yield).

I also fixed the one warning that clippy spits out, maybe we should not deny warnings in

renku-cli/flake.nix

Line 113 in 6d9fac2

cargoClippyExtraArgs = "--features user-doc --all-targets -- --deny warnings";

since there aren't any right now and having them fail CI is the best way to keep it that way.