refactor(executor): Separate executor code with different backends

[TianyiZhao1437]

📋 PR Title Format

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type(scope): concise message (max 50 chars)

Where:

• type is one of: feat, fix, docs, refactor, perf, test, chore.
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📝 Change Type

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• feat: New feature.
• fix: Bug fix.
• docs: Documentation only changes.
• refactor: A code change that neither fixes a bug nor adds a feature.
• perf: Performance improvement.
• test: Adding missing tests or correcting existing tests.
• chore: Maintenance tasks (e.g., updating dependencies).

💡 Description

Implement backend-awareness executors, as well as a common base executor class.
Refactor to use factory mode design to initialize.

Key Changes

1. Separate backend code in executor.
2. Use factory design to initialize executor.

🔗 Related Issues

• Closes [Feature]: Recator executor code to suit different device #246

✅ Checklist

Please ensure the following points are addressed before merging:

• I have performed a self-review of my own code.
• I have added/updated tests that prove my fix or feature works (if applicable).
• I have updated the documentation (if necessary).
• My code follows the project's style guidelines.