Improve mask merging and resizing

[cymoon59]

• Add support for merging multiple masks into a single binary mask
• Implement mask resizing to match target image dimensions
• Enhance error handling for invalid mask inputs

This commit enhances the UltralyticsMergeMasks class to handle multiple input masks, merge them into a single binary mask, and optionally resize the result to match a target image.

[kadirnar]

Thank you for the development. Have you tested it?