[spark] Refactor PaimonScan hierarchy to support flexible runtime filtering implementations

[kerwin-zk]

Purpose

• Created PaimonScanCommon abstract class to extract common functionality
• Moved PaimonScan to extend PaimonScanCommon
• Implemented SupportsRuntimeV2Filtering in PaimonScan
• This refactoring allows other classes to extend PaimonScanCommon and implement SupportsRuntimeFiltering interface independently
• Improves code reusability and extensibility for different runtime filtering strategies

This change enables better inheritance structure where multiple scan implementations can share common logic while having their own runtime filtering behavior.

Tests

CI

[YannByron]

+1