pub fn get_package_manager(
        repo_root: &AbsoluteSystemPath,
        package_json: &PackageJson,
    ) -> Result<Self, Error> {
        Self::read_package_manager(repo_root, package_json)
    }
Try to extract the package manager from package.json.
Package Manager will be read from package.json only using the file
system if the version is a URL and we need to invoke the binary it
points to for version information.
crates/turborepo-repository/src/package_manager/mod.rs