fix: extra byte read from chunk transfer

[xinsong-cui]

Issue #

Fixes #1285

Description of changes

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[ianbotsf]

Question: I feel pretty strongly that AwsChunkedSource.read should return the number of bytes which were read from the delegate source rather than the number of bytes written to the destination sink. Can we just return totalBytesTransferred - chunkReader.chunkMetadataBytes instead of storing it in a property? What do we need the total bytes transferred for (at least, as the output from read)?

[xinsong-cui]

We still need to return totalBytes for some of our tests:

smithy-kotlin/runtime/auth/aws-signing-tests/common/src/aws/smithy/kotlin/runtime/auth/awssigning/tests/AwsChunkedTestBase.kt

Line 445 in 444ff8a

val totalBytesExpected = encodedUnsignedChunkLength(CHUNK_SIZE_BYTES) + encodedUnsignedChunkLength(0) + "\r\n".length

If we not return the totalBytesTransferred, those tests will fail.

[lauzadis]

I'm pretty sure we can find a way around that, maybe by exposing the total bytes as some kind of test utility?

[xinsong-cui]

Manually added no-changelog label as changelog check somehow not passing

[github-actions]

Affected Artifacts

No artifacts changed size

[lauzadis]

I don't think adding a public API "for testing purposes only" is the best. Can we refactor this to make it internal-only, or otherwise refactor the tests?