Fix CustomModelData for paper

[1robie]

This pull request refactors and improves the handling of the CustomModelDataComponent across the codebase, with a particular focus on simplifying data structures and adding better support for Paper/Folia servers. The main changes include removing the use of Optional for component lists, improving data loading logic, and introducing Paper-specific implementations for custom model data components.

Refactoring and simplification of CustomModelDataComponent:

• Removed the use of Optional for the colors, flags, floats, and strings fields in CustomModelDataComponent, replacing them with non-optional lists and updating constructors and getters accordingly. This simplifies the API and usage throughout the codebase.
• Updated the apply method in CustomModelDataComponent to check for non-empty lists instead of using Optional.ifPresent, ensuring properties are only set when data is present.

Component loader improvements:

• Refactored SpigotCustomModelDataItemComponentLoader to remove all Optional usage, streamline list extraction, and add helper methods (getFloats, getBooleans, getStrings, getColors) for cleaner and more maintainable code. [1] [2]
• Added a new PaperCustomModelDataComponentLoader that extends the Spigot loader and constructs a Paper-specific CustomModelData using the Paper API, enabling enhanced support for Paper/Folia servers.
• Introduced a new PaperCustomModelDataComponent class that applies the Paper CustomModelData to item stacks.

General codebase cleanup:

• Removed the unused MenuItemStackFormMap class, cleaning up legacy or unnecessary code.

Plugin initialization logic:

• Modified the component registration logic to use the new PaperCustomModelDataComponentLoader when running on Paper or Folia, ensuring the correct loader is used based on the server type.