Handle GCS rate limit on manifest write contention

[wjones127]

We have essentially the same problem as in delta lake, where concurrent writers can hit a rate limit while trying to commit the manifest. We should handle the 429 as another writer beat us, rather than as a request error.

TODO: see if this applies to other object stores (S3, minio, Cloudflare R2, Azure blob)

See: delta-io/delta-rs#2451