refactor: splitting clap::Parser from Config

[forsaken628]

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Summary

The current Config takes on too many roles and is difficult to understand and maintain, in this PR Cmd is split from Config and dedicated to parsing commands. Also optimized the display of databend-query --help.

Tests

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

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 (please describe):

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This change is 

[BohuTANG]

Hi @forsaken628,

Making config loading easier is great! 👍

Please enhance this summary to clarify the intent behind this change and confirm whether it impacts our existing warehouse loading mechanisms, as we have different config loading approaches across various scenarios and want to avoid breaking changes.

cc @everpcpc to review.