Add S3/R2 sync check tool and split SHA256 management out of manage_v2.py#7947

atalman wants to merge 3 commits intopytorch:mainpytorch/test-infra:mainfrom

atalman:fix_s3_wheels_out_of_syncatalman/test-infra:fix_s3_wheels_out_of_syncCopy head branch name to clipboard