Fix incorrect checksum issue

[a-khanna]

This PR corrects a small byte array copying mistake in HashingHelper.

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• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
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What is the current behavior?

Issue Number: #373

What is the new behavior?

Correct checksums are generated.
For example, consistency can be verified using certUtil on windows with something like certutil -hashfile <filename> SHA256

Other information

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• Followed the code style guideline as described in CONTRIBUTING.md
• Verified that the change work in Release build configuration
• Checked all unit tests pass

[veler]

Hello,

Thank you very much for this fix! :) Should we update the Unit Tests?

[a-khanna]

@veler Hi, sorry for the late response.
I have added some test cases for checksums on a large file (2MB).
Personally, I avoid placing large files in the solution just to use them in test cases, so I have created a 2MB byte array within the test class here. But please let me know if you prefer testing this in another way.

[veler]

Thanks @a-khanna ! It looks great! 🎉🚀