Multi-part s3 uploads fail when using checksum

[avantgardnerio]

Describe the bug

with_checksum_algorithm() fails when used in with put_multipart_opts() on large files

To Reproduce

1. Set standard AWS env vars
2. Run test
3. observe:

message: "Checksum Type mismatch occurred, expected checksum Type: null, actual checksum Type: sha256

Expected behavior

It should write the file

Additional context

See PR for failing test

[thinkharderdev]

So there are a couple of issues with how multi-part upload is implemented:

1. The initial PUT request to CreateMultipartUpload must specify the checksum algo or else calling PutPart with the checksum will fail (eg set x-amz-checksum-algorithm: SHA256 on the request)
2. When calling CompleteMultipartUpload we need to send all the part checksums in the request (see `https://docs.aws.amazon.com/AmazonS3/latest/API/API_CompleteMultipartUpload.html)

So this means that we need to keep the checksums in the PartId for when we complete the upload