Function map_pull_request_evidence 

pub fn map_pull_request_evidence(
    repo: &str,
    pr_number: u32,
    pr_metadata: &PrMetadata,
    pr_files: &[PrFile],
    pr_reviews: &[Review],
    pr_commits: &[PrCommit],
) -> GovernedChange

Converts GitHub PR data into a platform-neutral GovernedChange.