implements first part of #6544 : restructure code to avoid handling user sandbox in TaskWorker, but download it directly in the scheduler DAG boostrap process. Just minor, changes of code from @novicecpp in #8645 plus rebasing
Also check that object is visible in S3 after uploading
What's Changed
- add checkS3Object and verify S3 upload with it by @belforte in #8740
- Download sandbox from s3 to scheduler by @belforte in #8743
- Stop downloadind user sandbox in tw by @belforte in #8745
Full Changelog: v3.241017...v3.241018