* feat: "product" and "variation" connections added to LineItem type
* chore: Coding standards met
* fix: GraphQLE2E helper updated to reflect schema changes
* chore: PHP 8.0 compliance met
* chore: Workflow codecoverage set to target PHP 7.4
* chore: WPCS compliance met
* fix: Huge refactor across schema and unit tests
* - add shipping_method loader in class-core-schema-filters.php
* - Update class-wc-db-loader.php to respect the new SHIPPING_METHOD loader with a `load_shipping_method_from_id()` function
* - Convert Shipping_Method_Connection_Resolver to extend AbstractConnectionResolver
* - Replace resolver for Shipping Methods connection. Remove use of `resolveNode` and replace the resolver with the new connection class `get_connection()` call
* chore: Factory class refactored.
* - update the function that registers Product Types to the Schema to use the value from the `get_enabled_product_types()` as the Type name and the key as the fieldName
* chore: PaymentGatewayQueriesTest refactored.
* chore: WPCS compliance met
* chore: Syntax error fixed.
Co-authored-by: Jason Bahl <jasonbahl@mac.com>
