feat(dm): Support Dameng (DM) SQL Parser and Bug Fixes

[Arlowen]

Summary

This Pull Request introduces comprehensive support for parsing Dameng (DM) database SQL statements. It includes the implementation of the DM dialect parser, lexer, and AST visitor logic, ensuring that DM-specific syntax is correctly parsed and formatted.

Additionally, this PR addresses several reported bugs related to the DM parser and enhances test coverage to ensure stability.

Detailed Changes

Features

• DM SQL Support: Added initial support for Dameng database parsing logic (DMLexer, DMStatementParser, DMAstVisitor).
• Test Coverage: Added detailed test cases for various DM SQL scenarios to verify parser accuracy.
• Import Refactoring: Optimized import statements across related classes for better code organization.

Bug Fixes

• SQL Parser Logic: Fixed parsing issues reported in [BUG] SQL解析报错 #6552, 请问数据库类型枚举中的dm是指达梦吗？如果是的话达梦TOP语句不支持，解析报错 #5026, and [BUG] 达梦sql解析失败 #6583.
• ALTER TABLE Support: Fixed an issue where ALTER TABLE options were not being preserved in the AST and SQL output, ensuring round-trip fidelity.

Related Issues

• Fixes [BUG] SQL解析报错 #6552
• Fixes 请问数据库类型枚举中的dm是指达梦吗？如果是的话达梦TOP语句不支持，解析报错 #5026
• Fixes [BUG] 达梦sql解析失败 #6583

Checklist

• Logic implementation for DM parser
• Unit tests added and verified locally
• Code style and imports cleaned up
• Verified bug fixes against reported issues

[CLAassistant]

All committers have signed the CLA.