Reduce memory usage for chunked artifact uploads to MinIO (#31325)

Reduce memory usage for chunked artifact uploads to MinIO (#31325)

When using the MinIO storage driver for Actions Artifacts, we found that
the chunked artifact required significantly more memory usage to both
upload and merge than the local storage driver. This seems to be related
to hardcoding a value of `-1` for the size to the MinIO client [which
has a warning about memory usage in the respective
docs](https://pkg.go.dev/github.com/minio/minio-go/v7#Client.PutObject).
Specifying the size in both the upload and merge case reduces memory
usage of the MinIO client.

Co-authored-by: Kyle D <kdumontnu@gmail.com>