Fix #13983: Improve custom option matching for multi-store imports

[satishashilwar]

• Modified _initOldCustomOptions() to include sort_order in existing option data
• Enhanced _findExistingOptionId() to match by type + sort_order first, then fallback to title matching
• This ensures options with same structure but different store titles are recognized as translations
• Fixes issue where multi-store CSV imports created duplicate options instead of proper translations

The fix maintains backward compatibility by keeping title-based matching as fallback.

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[satishashilwar]

@magento run all tests