library: Deserialize version and git commit hash from the rustup TOML manifests

[lambdageek]

The TOML manifest has these fields, but the PackageTargets type does not deserialize them:

[pkg.rust]
version = "1.88.0-nightly (e9f8103f9 2025-05-07)"
git_commit_hash = "e9f8103f93f8ce2fa2c15c0c6796ec821f8ae15d"

/// Package info.
#[derive(Debug, Serialize, Deserialize, PartialEq)]
pub struct PackageTargets {
    /// Maps targets onto package availability info.
    #[serde(rename = "target")]
    pub targets: HashMap<String, PackageInfo>,
}

This PR updates PackageTargets to include the version and git_commit_hash fields

Fixes #58