Add delete functionality for Metaobject Definitions

[mtylty]

This pull request extends the ShopifyToolkit::MetaobjectStatements module by adding the ability to delete metaobject definitions through the Shopify GraphQL API.

New functionality for deleting Shopify metaobject definitions:

• Method delete_metaobject_definition: Implements functionality to delete an existing metaobject definition by its type. The method includes built-in checks to skip deletion if the metaobject definition doesn't exist, providing user-friendly feedback. (lib/shopify_toolkit/metaobject_statements.rb)

Key features:

• Uses the metaobjectDefinitionDelete GraphQL mutation from Shopify's Admin API
• Includes proper error handling through the existing handle_shopify_admin_client_errors method
• Gracefully handles cases where the metaobject definition doesn't exist
• Follows the existing code patterns and conventions in the module
• Includes the log_time decorator for performance monitoring

Implementation details:

• Leverages the existing get_metaobject_definition_gid method to check for metaobject existence
• Uses the same GraphQL query structure and error handling patterns as other methods in the module
• Provides clear user feedback when attempting to delete non-existent metaobject definitions

[Copilot]

Pull Request Overview

This PR adds a new method to delete metaobject definitions via the Shopify GraphQL API.

• Adds method delete_metaobject_definition with pre-deletion checks
• Implements GraphQL deletion query with consistent error handling and performance logging

[Copilot]

[nitpick] Consider using a heredoc to define the multi-line GraphQL query for improved readability and easier maintenance.