fix: constraint multi-column ordering

[tianzhou]

This revives #17, which is reverted by #19

The addition is to change the testdata/diff/create_table/add_table_composite_keys test case so we can verify this issue before/after the fix.

Credit to @screenfluent for pushing this.

[Copilot]

Pull Request Overview

This PR fixes an issue with multi-column constraint ordering by ensuring constraint columns are sorted by their database position. The change restores the correct column ordering for unique, primary key, and foreign key constraints that was previously broken.

• Adds position-based sorting for constraint columns to preserve original database order
• Updates test data to verify the fix with reordered UNIQUE constraint columns
• Includes special handling to maintain existing partitioned table primary key logic

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/ir/inspector.go	Adds position-based sorting logic for constraint columns and helper function
testdata/diff/create_table/add_table_composite_keys/plan.txt	Updates expected output with reordered UNIQUE constraints for testing
testdata/diff/create_table/add_table_composite_keys/plan.sql	Updates SQL test case with reordered UNIQUE constraints
testdata/diff/create_table/add_table_composite_keys/plan.json	Updates JSON test case and version number
testdata/diff/create_table/add_table_composite_keys/new.sql	Updates target schema with reordered UNIQUE constraints
testdata/diff/create_table/add_table_composite_keys/diff.sql	Updates diff output with reordered UNIQUE constraints

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[tianzhou]

cc @screenfluent