feat(catalog): add LoadTableSchema interface

[dalingmeng]

Purpose

Catalog add loadTableSchema interface.

Tests

file_system_catalog_test.cpp : TEST(FileSystemCatalogTest, TestValidateTableSchema);

API and Format

Documentation

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[Copilot]

Pull request overview

This PR adds a LoadTableSchema interface to the Catalog API, allowing users to retrieve table schema metadata. It introduces a new public Schema class that wraps TableSchema and provides access to table metadata through a simplified interface.

Key changes:

• Adds LoadTableSchema method to the Catalog interface that returns schema information for a specified table
• Introduces a new public Schema class in include/paimon/schema/schema.h that provides accessors for table metadata
• Adds GetArrowSchema() method to TableSchema to export schema to Arrow C Data Interface format

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
include/paimon/catalog/catalog.h	Adds LoadTableSchema pure virtual method to Catalog interface
include/paimon/schema/schema.h	Defines new public Schema class with metadata accessors
src/paimon/core/catalog/file_system_catalog.h	Implements LoadTableSchema and exposes GetFileSystem/Warehouse methods
src/paimon/core/catalog/file_system_catalog.cpp	Implements LoadTableSchema by delegating to Schema::MakeImpl
src/paimon/core/schema/schema.cpp	Implements Schema class with delegation to internal TableSchema
src/paimon/core/schema/table_schema.h	Declares GetArrowSchema method
src/paimon/core/schema/table_schema.cpp	Implements GetArrowSchema using Arrow C Data Interface export
src/paimon/core/catalog/file_system_catalog_test.cpp	Adds comprehensive test coverage for LoadTableSchema functionality
src/paimon/CMakeLists.txt	Adds schema.cpp to build configuration

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[lxy-9602]

+1