Add non-zero check for incremental upload buffer sizes

[mansi153]

Add non-zero check for upload buffer-sizes.

This is done so that we avoid runtime exceptions for invalid sized buffers and division by 0 during capacity calculations in current or future incremental uploads. The buffer_size currently is derived from write-part-size. We have a check for read/write part-sizes being in the range [5MiB, 5GiB] in the CrtClientConfig. However, there are some tests and testing trait-implementations which don't do the same validation and hence need explicit checks in the upload constructor.

Does this change impact existing behavior?

No.

Does this change need a changelog entry? Does it require a version change?

No, minor code enhancement entry.

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[muddyfish]

Could you include the error message that's displayed when this fails in the description?

[passaro]

This seems the wrong place to check. Why not UploaderConfig::new (where buffer_size is passed)?

Also, the message here should be related to this type, rather than user-facing. --write-part-size is a CLI argument and should be validated elsewhere.

[c-hagem]

Maybe we should consider making the size (NonZero)[https://doc.rust-lang.org/std/num/type.NonZeroU32.html]?