[python] Optimize BLOB write performance

[discivigour]

What is the purpose of the change?

Improve Python BLOB write performance by reducing CRC and Arrow row-selection overhead.

Brief change log

• Use isal_zlib.crc32 when available, with zlib as the fallback.
• Reuse the original Arrow batch when all rows belong to one partition/bucket.
• Use zero-copy Arrow slice for contiguous partition/bucket groups.
• Keep Arrow take for non-contiguous groups.
• Add coverage for CRC compatibility and all three Arrow grouping paths.

Performance

A 60 GB BLOB write test improved as follows:

Data size	Before	After	Elapsed-time reduction
60 GB	178.984 s	132.871 s	25.76%

The elapsed time decreased by 46.113 seconds, from 178.984 seconds to 132.871 seconds.

Tests

• Verify the fallback CRC written to BLOB records matches standard zlib.crc32.
• Verify isal_zlib and zlib produce byte-identical BLOB records.
• Verify full batches are passed through without Arrow take.
• Verify contiguous groups use zero-copy Arrow slice.
• Verify non-contiguous groups continue to use Arrow take.
• Verify partitioned BLOB data can be written and read end to end.