feat(bigtable): add validation for checksum in stream processing

[mpeddada1]

With this change, we should also be able to address the ChecksumMismatch conformance test failure.

[codecov]

Codecov Report

❌ Patch coverage is 94.08284% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.94%. Comparing base (0f0a7cf) to head (f6e78a6).
⚠️ Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
google/cloud/bigtable/internal/const_buffer.cc	0.00%	10 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15770      +/-   ##
==========================================
- Coverage   92.95%   92.94%   -0.01%     
==========================================
  Files        2448     2453       +5     
  Lines      226434   226598     +164     
==========================================
+ Hits       210483   210618     +135     
- Misses      15951    15980      +29     

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[scotthart]

For all the new files created, update the Copyright year to 2025.

[scotthart]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces checksum validation for stream processing in Bigtable, which is a valuable addition for ensuring data integrity. The changes include new utility files for CRC32C calculation and buffer management, with a performance-aware implementation for CRC32C. The core validation logic is implemented in PartialResultSetSource, and the build files and tests have been updated accordingly. The tests are now more robust, using calculated checksums instead of hardcoded values, and a new test for checksum mismatches has been added. Overall, the changes are well-implemented. I have one suggestion to improve error handling consistency.