Exporter should check the crc hash before uploading #3513
Description
Describe the bug
Currently, the exporter uploads a file no matter if the file has changed or not.
Expected behaviour
We want to only upload if the file has a different file hash.
Additional context
Recently with #3491 the all.zips are now reproducable - hashes remain the same across runs. This means we can check the hash and avoid uploading if nothing has changed. This also prevents a new generation from being added to bucket history, making it easier for users to avoid downloading the same files.