[python] Fix DECIMAL Arrow predicates across scales

[wangzhigang1999]

Purpose

On PyArrow 19.0.1, filtering a DECIMAL(15, 2) column with < Decimal('2') can return no rows where 1.00 and 1.01 should match. Arrow evaluates the literal at a different scale from the column.

Pass the physical Arrow schema into predicate conversion and build exact DECIMAL comparisons at the column's scale. This covers file pushdown and post-read batch filtering, including range, IN, and BETWEEN predicates. The bound is never rounded into an equality match.

Fixes #10316. The underlying Arrow behavior is tracked in apache/arrow#41011.

Tests

• Targeted predicate and read tests on PyArrow 19.0.1 and 22.0.0: 213 passed and 32 subtests passed per version.
• Ruff format/check and Black -S --check passed for the new files and changed code; Pyright reported no errors in the new module.
• A three-round local SF10 read benchmark on PyArrow 22.0.0 passed 48/48 correctness checks. Measured DECIMAL read times showed no material regression.

[Copilot]

Copilot review overview

🟢 Approval recommended

The implementation correctly preserves DECIMAL bound semantics and includes strong regression coverage.

Review effort: Balanced
Findings: None

What changed in this PR

Fixes incorrect DECIMAL filtering when Arrow literals and columns use different scales.

Changes:

• Generates exact, scale-aware Arrow DECIMAL expressions.
• Supplies schemas during pushdown and post-read filtering.
• Adds comprehensive comparison, range, set, evolution, and integration tests.

File	Description
common/​decimal_arrow_predicate.py	Implements exact DECIMAL expression generation.
common/​predicate.py	Adds schema-aware DECIMAL conversion.
read/​split_read.py	Supplies physical schemas for pushdown.
read/​reader/​filter_record_batch_reader.py	Uses batch schemas for residual filtering.
tests/​decimal_predicate_test.py	Covers DECIMAL predicate behavior comprehensively.
tests/​where_parser_test.py	Adds SQL range regression coverage.

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