Allow S3 direct uploads with checksum algorithms other than MD5

[qqmyers]

Dataverse itself supports several checksum algorithms in addition to MD5, but the initial S3 direct upload API implementation hardcoded the algorithm to md5 (partly for simplicity and partly because md5 would be quicker to compute for large files).

DANS is now planning to use the API to migrate datafiles where they are computing/have computed SHA-1 hashes. Given the underlying support in Dataverse for SHA-1, removing the limitation of the api is straight-forward. I'll submit a PR that maintains backward compatibility and update documentation in #7596 to match.