feat(storage): Introduce unified checksum options and deprecate old options

[v-pratap]

Introduces unified enum-based UploadChecksumValidationOption and DownloadChecksumValidationOption and deprecates the old bool-based EnableMD5ValidationOption and EnableCrc32cValidationOption.

[gemini-code-assist]

Code Review

This pull request introduces UploadChecksumValidationOption and DownloadChecksumValidationOption to configure checksum algorithms, deprecating several older validation options. It also updates AsyncWriterConnectionImpl::Finalize to support manual expected checksums and adds corresponding unit tests and examples. The review feedback highlights a critical issue where non-appendable uploads only check current_options instead of merged options, which would cause pre-computed checksums specified at the start of the upload to be ignored during finalization.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.27%. Comparing base (e493b2d) to head (6c92722).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16260      +/-   ##
==========================================
- Coverage   92.27%   92.27%   -0.01%     
==========================================
  Files        2214     2214              
  Lines      206505   206518      +13     
==========================================
+ Hits       190556   190558       +2     
- Misses      15949    15960      +11     

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[kalragauri]

In the old boolean system, a user could theoretically have passed DisableCrc32cChecksum(false) and DisableMD5Hash(false) to force the client to compute and validate both hashes. If that use case is valid, we may need a kBoth enum member.