fix(query): add partition write regression tests

[KKould]

I hereby agree to the terms of the CLA available at: https://docs.databend.com/dev/policies/cla/

Summary

This test-only PR expands coverage for physical partition metadata and hash write layout edge cases:

• Verify that a MERGE moving a row across a partition boundary preserves exact metadata for pruning.
• Verify that missing DEFAULT and stored computed partition columns are materialized before hash routing and layout.
• Verify that nullable partition values remain isolated by block and support IS NULL pruning.
• Verify that multi-table INSERT keeps each target table's partition expression and metadata independent.

No production behavior is changed.

Current write-path support observed while adding these tests:

Write path	Current status
INSERT SELECT / VALUES / OVERWRITE / CTAS	Uses the common table write layout
COPY INTO table	Uses the common local write layout; distributed cross-node partition routing is a separate concern
Multi-table INSERT	Uses per-target chunk transforms rather than the common hash write layout
REPLACE INTO	Uses an independent replace pipeline
MERGE unmatched INSERT	Uses the mutation-specific append pipeline rather than the common hash write layout
Materialized-view refresh	Inherits either the INSERT or MERGE path selected by its refresh strategy

This PR intentionally adds coverage only. Unifying the remaining write paths requires separate design work rather than statement-specific fixes.

Tests

• Unit Test
• Logic Test
• Benchmark Test
• No Test - Explain why

Added or extended these sqllogictest files:

• tests/sqllogictests/suites/base/09_fuse_engine/09_0054_partition_by.test
• tests/sqllogictests/suites/base/09_fuse_engine/09_0100_insert_multi_table.test
• tests/sqllogictests/suites/ee/02_computed_column/02_0001_partition_by.test

Local execution was skipped; CI will run the logic-test suites.

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other: test coverage

AI assistance

• AI usage: An AI coding agent helped inspect the write paths, draft the logic-test coverage, and prepare the PR summary. The responsible human reviewed the final test diff and selected the submission scope.
• Responsible human: @KKould
• The responsible human has read every line of this diff and can explain each change

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This change is 

[sundy-li]

发现 1 个阻塞问题：

• [P1] 修正 stored computed column 的表达式类型 — tests/sqllogictests/suites/ee/02_computed_column/02_0001_partition_by.test:26
p 声明为 INT（Int32），但 Databend 将 id % 2 推导为 Int16，因此 CREATE TABLE 在 EE sqllogic CI 中直接失败：expected computed column expression have type Int32 NULL, but id % 2 has type Int16 NULL。请将表达式显式转换为 INT（例如 p INT AS ((id % 2)::INT) STORED），或让列类型与表达式类型一致，并重新运行相关 CI。

其余 diff 仅为测试新增；当前 linux / sqllogic / ee 和 ready 检查失败，所以本次 review 不予 approve。

[sundy-li]

Reviewed the latest head 4dd3ff2. The previous computed-column type issue is fixed by using SMALLINT, and all required CI checks pass, including linux / sqllogic / ee. No remaining blocking issues.