hash.ChecksumMismatch now carries the requested algorithm (CRC32, CRC32C,
SHA1, SHA256, CRC64NVME), and toAPIError renders it S3-style:
The CRC32 you specified did not match the calculated checksum.
instead of the generic "The provided 'x-amz-checksum' header does not match
what was computed.", for all four mismatch construction sites (streaming
reader, trailing-checksum decode, and both Checksum.Matches paths). Mirrors
the wording already shipped for CompleteMultipartUpload in #225.
Fixes#226
Paris Yu
968c30238c