Revert order and product controllers to use WP Post queries directly.

This commit revert some of the changes added in #27735 because wc_get_products and wc_get_orders is not fully compitable with API controller queries. Since we are close to release 4.9, its better to revert and fix them properly then rush a fix. This undones some the performance improvements we acheived in 27735, in favor of more stability, hopefully we will be able to restore this soon.

includes/rest-api/Controllers/Version3/class-wc-rest-orders-controller.php

@@ -25,25 +25,6 @@ class WC_REST_Orders_Controller extends WC_REST_Orders_V2_Controller {
 	 */
 	protected $namespace = 'wc/v3';
 
-
-	/**
-	 * Get Orders.
-	 *
-	 * @param  array $query_args Query args.
-	 *
-	 * @return array Products.
-	 */
-	protected function get_objects( $query_args ) {
-		$query_args['paginate'] = true;
-		$results                = wc_get_orders( $query_args );
-
-		return array(
-			'objects' => $results->orders,
-			'total'   => $results->total,
-			'pages'   => $results->max_num_pages,
-		);
-	}
-
 	/**
 	 * Calculate coupons.
 	 *

includes/rest-api/Controllers/Version3/class-wc-rest-products-controller.php

@@ -220,25 +220,6 @@ class WC_REST_Products_Controller extends WC_REST_Products_V2_Controller {
 		return $args;
 	}
 
-	/**
-	 * Get products.
-	 *
-	 * @param  array $query_args Query args.
-	 *
-	 * @return array Products.
-	 */
-	protected function get_objects( $query_args ) {
-		$query_args['paginate'] = true;
-		$query_args['return']   = 'objects';
-		$results                = wc_get_products( $query_args );
-
-		return array(
-			'objects' => $results->products,
-			'total'   => $results->total,
-			'pages'   => $results->max_num_pages,
-		);
-	}
-
 	/**
 	 * Set product images.
 	 *