feat(storage): Add full object checksum validation for appendable uploads

[v-pratap]

No description provided.

[gemini-code-assist]

Code Review

This pull request implements dynamic CRC32C validation for appendable object uploads by updating the connection and writer logic to initialize hash functions from RPC response metadata. It also adds a stateful constructor to the CRC32C hash function. Feedback highlights a critical regression where a large suite of existing integration tests was deleted and replaced with experimental code. Additional suggestions include adding defensive checks for CRC32C field presence, utilizing existing library thread management instead of a custom thread pool in tests, and using environment variables instead of hardcoded strings for test configuration.

[codecov]

Codecov Report

❌ Patch coverage is 91.59664% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.71%. Comparing base (a899f46) to head (8167423).

Files with missing lines	Patch %	Lines
...d/storage/internal/async/writer_connection_impl.cc	55.00%	9 Missing ⚠️
...le/cloud/storage/internal/async/connection_impl.cc	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16110      +/-   ##
==========================================
- Coverage   92.71%   92.71%   -0.01%     
==========================================
  Files        2353     2353              
  Lines      218986   219098     +112     
==========================================
+ Hits       203031   203129      +98     
- Misses      15955    15969      +14     

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[kalragauri]

Is it possible that: if a connection retry is triggered during the session, and the server's reported persisted_size causes a resend that overlaps with (but is not exactly aligned to) the client's previous chunk boundaries, the request fails?

[v-pratap]

Yes, the request will fail if we try to send overlapping data.
I think the server strictly requires the next write to start exactly at the persisted_size it has saved.