feat(storage): enable CRC32C validation by default in transfer manager

[thiyaguk09]

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• Ensure the tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

Fixes #<issue_number_goes_here> 🦕

[gemini-code-assist]

Code Review

This pull request updates the downloadFileInChunks method in TransferManager to enable CRC32C validation by default and ensures that validation is performed only on the final assembled file rather than on individual chunks. The review feedback suggests refining the logic for defaulting the validation method to ensure that explicitly provided validation strings are respected instead of being coerced to 'crc32c'.