Multi-chunk Upload Without `contentLength` Can Hang When `fileSize % chunkSize != 0`

[danielbankhead]

A multi-chunk resumable upload hangs when the chunkSize is not evenly divisible by the file size when a contentLength is not provided.

ACs:

• Fix upload logic for this scenario
• Fix unit test(s)
• Add integration tests for the following scenarios:
  • fileSize % chunkSize != 0
  • fileSize < chunkSize