Stop tar.gz update downloads after unpack failure

[ryanfowler]

Summary

• Stop reading the tar.gz update stream as soon as the unpack task ends early
• Surface the unpack task error immediately instead of draining the remaining response body
• Add a regression test that feeds an unsafe first tar entry followed by a long tail stream

Testing

• cargo test --all-features unpack_tar_gz_response_stops_downloading_after_unpack_fails
• cargo clippy --locked --all-targets --all-features -- -D warnings