Convert as much scripts as possible to xtask

The shell scripts start to get more/too complex. We should migrate them to xtask as modules (or even libraries). Ideally, the only remaining script would be `setup.sh` to install enough things for xtask to run (probably rustup and build-essential).

Can use [cargo_toml](https://crates.io/crates/cargo_toml) to parse `Cargo.toml` files. Description of configurations for `cargo check` and `cargo test` (from which `cargo clippy` are derived) can be in `package.metadata` like for `package.metadata.docs.rs` from which `cargo doc` is derived. Note that `cargo fmt` is always the same.

Other useful crates: [git2](https://crates.io/crates/git2), [semver](https://crates.io/crates/semver).

Related tasks:
- #448
- #583

We might want to also make use of [cargo-script](https://rust-lang.github.io/rust-project-goals/2024h2/cargo-script.html) to keep the script feeling.

In addition to the logic in `ci-changelog.sh` regarding `Cargo.toml` files, an additional rule should be that `publish = false` crate should not use `version` in local dependencies (i.e. with `path`).

Another rule could be that optional dependencies should not define any features. The features should be added by the features that enable the dependency.