Implement automatic plugin ID namespacing for FlowDrop node processors

Summary

Implement automatic namespacing of FlowDropNodeProcessor plugin IDs to prevent ID collisions when multiple modules define plugins with the same base ID. Plugin IDs are now automatically prefixed with their provider module name.

Business Value

• Prevents plugin ID conflicts between contrib modules
• Enables multiple modules to provide similarly-named processors without collision
• Provides clear provenance for each plugin in debugging scenarios
• Follows Drupal best practices for plugin namespacing

Technical Details

• Plugin IDs now follow the format {provider_module}:{original_id}
• Example: A plugin with ID "text_input" in module "flowdrop_node_processor" becomes "flowdrop_node_processor:text_input"
• Helper methods added to plugin manager for ID manipulation
• Update hooks provided for automatic migration of existing configurations

Migration Support

Existing sites will have their configurations automatically migrated via update hooks. No manual intervention required for the upgrade path.