Label and Select Menu support for Modals

[valzargaming]

This pull request introduces support for Discord's new Label component and updates the modal component structure to reflect Discord's latest standards. The main changes include the addition of the Label component, deprecation of ActionRow usage in modals, and updates to select menus and text inputs to support modal requirements. These changes modernize the component system and improve compatibility with Discord's evolving API.

Component System Updates

• Added the new Label component as a top-level container for modals, including its implementation in both builders (Label.php) and message parts (Label.php). [1] [2]
• Registered TYPE_LABEL in the component type constants and mapping, enabling its use throughout the codebase. [1] [2]

Modal Structure Changes

• Deprecated the use of ActionRow as a top-level container in modals; documentation and code comments now recommend using Component::Label instead. [1] [2]
• Updated interaction handling logic to support both Label and ActionRow containers when processing modal submissions.

Select Menu and Text Input Enhancements

• Added support for required select menus in modals, including validation and serialization logic, and exposed setRequired on StringSelect. [1] [2] [3]
• Deprecated the label property on TextInput for modals, making it optional and updating constructors and serialization accordingly. [1] [2] [3] [4] [5]

Minor Improvements

• Improved docblocks and error handling for select menu validation, and clarified usage contexts for components. [1] [2] [3] [4]